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A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a
laboratory instrument
laboratory instrument
used to examine objects that are too small to be seen by the
naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision ...
.
Microscopy Microscopy is the technical field of using microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look (at); examine, inspect') is a laboratory instrument used to examine objects that are too small to b ...

Microscopy
is the
science Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe."... modern science is a discovery as well as an invention. ...

science
of investigating small objects and structures using a microscope.
Microscopic The microscopic scale (from , ''mikrós'', "small" and σκοπέω, ''skopéō'' "look") is the scale of objects and events smaller than those that can easily be seen by the naked eye Naked eye, also called bare eye or unaided eye, is the pr ...

Microscopic
means being invisible to the eye unless aided by a microscope. There are many types of microscopes, and they may be grouped in different ways. One way is to describe the method an instrument uses to interact with a sample and produce images, either by sending a beam of
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nan ...

light
or
electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one elementary charge. Electrons belong to the first generation (particle physics), generation of the lepton particle family, and are general ...

electron
s through a sample in its
optical path The path that a light ray follows as it passes through an optical medium or system is often called the optical path. The physical length of an optical device can be reduced to less than the length of the optical path by using folded optics. The ...
, by detecting
photon emission
photon emission
s from a sample, or by scanning across and a short distance from the surface of a sample using a probe. The most common microscope (and the first to be invented) is the
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine ob ...
, which uses
lens A lens is a transmissive optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, s ...

lens
es to
refract In physics, refraction is the change in direction of a wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
visible light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nano ...
that passed through a thinly sectioned sample to produce an observable image. Other major types of microscopes are the
fluorescence microscope A fluorescence microscope is an that uses instead of, or in addition to, , , and or , to study the properties of organic or substances. "Fluorescence microscope" refers to any microscope that uses fluorescence to generate an image, whether ...

fluorescence microscope
,
electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a high ...

electron microscope
(both the
transmission electron microscope . The polio virus is 30 nm in diameter. Transmission electron microscopy (TEM) is a microscopy Microscopy is the technical field of using microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look ( ...

transmission electron microscope
and the
scanning electron microscope A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...
) and various types of
scanning probe microscope Scanning probe microscopy (SPM) is a branch of microscopy Microscopy is the technical field of using microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory inst ...
s.


History

Although objects resembling lenses date back 4,000 years and there are
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...

Greek
accounts of the optical properties of water-filled spheres (5th century BC) followed by many centuries of writings on optics, the earliest known use of simple microscopes (
magnifying glass A magnifying glass is a Lens (optics)#Types of simple lenses, convex lens that is used to produce a magnification, magnified image of an object. The lens (optics), lens is usually mounted in a frame with a handle. A magnifying glass can be used ...

magnifying glass
es) dates back to the widespread use of lenses in
eyeglasses Glasses, also known as eyeglasses or spectacles, are vision eyewear, consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known ...

eyeglasses
in the 13th century. The earliest known examples of compound microscopes, which combine an
objective lens Several objective lenses on a microscope. In optical engineering, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be a single lens A ...
near the specimen with an
eyepiece An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as Optical telescope, telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks t ...
to view a
real image{{citations needed, date=June 2019 File:realimageondetector.svg, 384px, Producing a real image. Each region of the detector or retina indicates the light produced by a corresponding region of the object. In optics, an ''image'' is defined as the ...

real image
, appeared in Europe around 1620. The inventor is unknown, even though many claims have been made over the years. Several revolve around the spectacle-making centers in the
Netherlands ) , national_anthem = ( en, "William of Nassau") , image_map = EU-Netherlands.svg , map_caption = , image_map2 = BES islands location map.svg , map_caption2 = , image_map3 ...

Netherlands
, including claims it was invented in 1590 by
Zacharias Janssen Zacharias Janssen (); also Zacharias Jansen or Sacharias Jansen; 1585 – pre-1632) was a Dutch spectacle-maker who lived most of his life in Middelburg. He is associated with the invention of the first optical telescope and/or the first tru ...

Zacharias Janssen
(claim made by his son) or Zacharias' father, Hans Martens, or both, claims it was invented by their neighbor and rival spectacle maker,
Hans Lippershey Hans Lipperhey (circa 1570 – buried 29 September 1619), also known as Johann Lippershey or Lippershey, was a German-Dutch spectacle-maker. He is commonly associated with the invention of the telescope, because he was the first one who tried to ...
(who applied for the first
telescope A telescope is an optical instrument An optical instrument (or "optic" for short) is a device that processes light waves (or photons), either to enhance an image for viewing or to analyze and determine their characteristic properties. Common ...

telescope
patent in 1608), and claims it was invented by
expatriate An expatriate (often shortened to expat) is a person residing in a country other than their native country. In common usage, the term often refers to professionals, skilled workers, or artists taking positions outside their home country, eit ...
Cornelis Drebbel Cornelis Jacobszoon Drebbel ( ) (1572 – 7 November 1633) was a Dutch engineer and inventor. He was the builder of the first navigable submarine in 1620 and an innovator who contributed to the development of measurement and control systems, optics ...
, who was noted to have a version in London in 1619.
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (; 15 February 1564 – 8 January 1642) was an Italian astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the ...

Galileo Galilei
(also sometimes cited as compound microscope inventor) seems to have found after 1610 that he could close focus his telescope to view small objects and, after seeing a compound microscope built by Drebbel exhibited in Rome in 1624, built his own improved version. Giovanni Faber coined the name ''microscope'' for the compound microscope Galileo submitted to the
Accademia dei Lincei The Accademia dei Lincei (; literally the "Academy An academy (Attic Greek: Ἀκαδήμεια; Koine Greek Ἀκαδημία) is an institution of secondary education, secondary or tertiary education, tertiary higher education, higher learning, ...
in 1625 (Galileo had called it the ''occhiolino'' 'little eye').


Rise of modern light microscopes

The first detailed account of the
microscopic anatomy Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Mol ...

microscopic anatomy
of organic tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's ''L'occhio della mosca'', or ''The Fly's Eye''. The microscope was still largely a novelty until the 1660s and 1670s when naturalists in Italy, the Netherlands and England began using them to study biology. Italian scientist
Marcello Malpighi Marcello Malpighi (10 March 1628 – 30 November 1694) was an Italians, Italian biologist and physician, who is referred to as the "Founder of microscopical anatomy, histology & Father of physiology and embryology". Malpighi's name is borne by se ...
, called the father of
histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

histology
by some historians of biology, began his analysis of biological structures with the lungs. The publication in 1665 of
Robert Hooke Robert Hooke FRS FRS may also refer to: Government and politics * Facility Registry System, a centrally managed Environmental Protection Agency database that identifies places of environmental interest in the United States * Family Resources ...
's ''
Micrographia ''Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses. With Observations and Inquiries Thereupon.'' is a historically significant book by Robert Hooke Robert Hooke FRS (;  – 3 March 1703) wa ...

Micrographia
'' had a huge impact, largely because of its impressive illustrations. A significant contribution came from
Antonie van Leeuwenhoek Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () *Dutch language , spoken in Belgium ...
who achieved up to 300 times magnification using a simple single lens microscope. He sandwiched a very small glass ball lens between the holes in two metal plates riveted together, and with an adjustable-by-screws needle attached to mount the specimen. Then, Van Leeuwenhoek re-discovered
red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...

red blood cell
s (after
Jan Swammerdam Jan Swammerdam (February 12, 1637 – February 17, 1680) was a Netherlands, Dutch biologist and microscopist. His work on insects demonstrated that the various phases during the life of an insect—Egg (biology), egg, larva, pupa, and adult—a ...

Jan Swammerdam
) and
spermatozoa A spermatozoon (pronounced , alternate spelling spermatozoön; plural spermatozoa; from grc, σπέρμα ("seed") and grc, ζῷον ("living being")) is a motile Motility is the ability of an organism In biology, an organism (from An ...
, and helped popularise the use of microscopes to view biological ultrastructure. On 9 October 1676, van Leeuwenhoek reported the discovery of micro-organisms. The performance of a light microscope depends on the quality and correct use of the condensor lens system to focus light on the specimen and the objective lens to capture the light from the specimen and form an image. Early instruments were limited until this principle was fully appreciated and developed from the late 19th to very early 20th century, and until electric lamps were available as light sources. In 1893
August Köhler August Karl Johann Valentin Köhler (March 4, 1866 – March 12, 1948) was a German professor and early staff member of Carl Zeiss AG Carl Zeiss AG (), branded as ZEISS, is a German manufacturer of optical systems and optoelectronics, found ...

August Köhler
developed a key principle of sample illumination, Köhler illumination, which is central to achieving the theoretical limits of resolution for the light microscope. This method of sample illumination produces even lighting and overcomes the limited contrast and resolution imposed by early techniques of sample illumination. Further developments in sample illumination came from the discovery of
phase contrastPhase-contrast imaging is a method of imaging that has a range of different applications. It exploits differences in the refractive index In optics, the refractive index (also known as refraction index or index of refraction) of a optical medium, m ...
by
Frits Zernike Frits Zernike (; 16 July 1888 – 10 March 1966) was a Dutch physicist and winner of the Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profi ...
in 1953, and
differential interference contrast Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast (NIC) or Nomarski microscopy, is an optical microscopy technique used to enhance the contrast in unstained, transparent samples. DIC works on the p ...
illumination by
Georges NomarskiGeorges (Jerzy) Nomarski (January 6, 1919 – 1997) was a Polish and naturalized-French physicist and optics theoretician. Creator of differential interference contrast (DIC) microscopy, the method is widely used to study live biological specimens ...
in 1955; both of which allow imaging of unstained, transparent samples.


Electron microscopes

In the early 20th century a significant alternative to the light microscope was developed, an instrument that uses a beam of
electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one elementary charge. Electrons belong to the first generation (particle physics), generation of the lepton particle family, and are general ...

electron
s rather than
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nan ...

light
to generate an image. The German physicist,
Ernst Ruska Electron microscope constructed by Ernst Ruska in 1933 Ernst August Friedrich Ruska (; 25 December 1906 – 27 May 1988) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizen ...
, working with electrical engineer
Max Knoll Max Knoll (17 July 1897 – 6 November 1969) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also ...
, developed the first prototype electron microscope in 1931, a
transmission electron microscope . The polio virus is 30 nm in diameter. Transmission electron microscopy (TEM) is a microscopy Microscopy is the technical field of using microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look ( ...

transmission electron microscope
(TEM). The transmission electron microscope works on similar principles to an optical microscope but uses electrons in the place of light and electromagnets in the place of glass lenses. Use of electrons, instead of light, allows for much higher resolution. Development of the transmission electron microscope was quickly followed in 1935 by the development of the
scanning electron microscope A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...
by
Max Knoll Max Knoll (17 July 1897 – 6 November 1969) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also ...
. Although TEMs were being used for research before WWII, and became popular afterwards, the SEM was not commercially available until 1965. Transmission electron microscopes became popular following the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
. Ernst Ruska, working at
Siemens Siemens AG ( ) is a German multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multinational state, ...

Siemens
, developed the first commercial transmission electron microscope and, in the 1950s, major scientific conferences on electron microscopy started being held. In 1965, the first commercial scanning electron microscope was developed by Professor Sir
Charles Oatley Sir Charles William Oatley OBE, FRS FREng Fellowship of the Royal Academy of Engineering (FREng) is an award and Scholarship, fellowship for engineers who are recognised by the Royal Academy of Engineering as being the best and brightest engi ...
and his postgraduate student Gary Stewart, and marketed by the Cambridge Instrument Company as the "Stereoscan". One of the latest discoveries made about using an electron microscope is the ability to identify a virus. Since this microscope produces a visible, clear image of small organelles, in an electron microscope there is no need for reagents to see the virus or harmful cells, resulting in a more efficient way to detect pathogens.


Scanning probe microscopes

From 1981 to 1983
Gerd Binnig Gerd Binnig (; born 20 July 1947) is a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German natio ...
and
Heinrich Rohrer Heinrich Rohrer (6 June 1933 – 16 May 2013) was a Swiss physicist A physicist is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of interest. In ...
worked at
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
in ,
Switzerland , french: Suisse(sse), it, svizzero/svizzera or , rm, Svizzer/Svizra , government_type = Federalism, Federal semi-direct democracy under an assembly-independent Directorial system, directorial republic , leader_title1 = Fe ...

Switzerland
to study the
quantum tunnelling Quantum tunnelling or tunneling (US) is the quantum mechanical Quantum mechanics is a fundamental theory A theory is a reason, rational type of abstraction, abstract thinking about a phenomenon, or the results of such thinking. The proce ...
phenomenon. They created a practical instrument, a
scanning probe microscope Scanning probe microscopy (SPM) is a branch of microscopy Microscopy is the technical field of using microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory inst ...
from quantum tunnelling theory, that read very small forces exchanged between a probe and the surface of a sample. The probe approaches the surface so closely that electrons can flow continuously between probe and sample, making a current from surface to probe. The microscope was not initially well received due to the complex nature of the underlying theoretical explanations. In 1984 Jerry Tersoff and D.R. Hamann, while at AT&T's Bell Laboratories in
Murray Hill, New Jersey Murray Hill is an unincorporated community File:Entering Heinola, Minnesota.jpg, Sign at Heinola, Minnesota, Heinola, an unincorporated community in Otter Tail County, Minnesota An unincorporated area is a region not governed by a local munici ...
began publishing articles that tied theory to the experimental results obtained by the instrument. This was closely followed in 1985 with functioning commercial instruments, and in 1986 with Gerd Binnig, Quate, and Gerber's invention of the
atomic force microscope Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy Scanning probe microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans ...
, then Binnig's and Rohrer's Nobel Prize in Physics for the SPM. New types of scanning probe microscope have continued to be developed as the ability to machine ultra-fine probes and tips has advanced.


Fluorescence microscopes

The most recent developments in light microscope largely centre on the rise of
fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection (physics), reflection, and attenuation or absorption (electromagnetic radiation), absorption, to study the properties ...

fluorescence microscopy
in
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
. During the last decades of the 20th century, particularly in the post-
genomic Genomics is an interdisciplinary field of focusing on the structure, function, evolution, mapping, and editing of s. A genome is an organism's complete set of , including all of its genes as well as its hierarchical, three-dimensional structur ...

genomic
era, many techniques for fluorescent
staining specimen, sandwiched between a glass microscope slide. Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (the study of tissue under the ...
of cellular structures were developed. The main groups of techniques involve targeted chemical staining of particular cell structures, for example, the chemical compound
DAPI DAPI (pronounced 'DAPPY', /ˈdæpiː/), or 4′,6-diamidino-2-phenylindole, is a fluorescent light. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescenc ...

DAPI
to label
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
, use of antibodies conjugated to fluorescent reporters, see
immunofluorescence Immunofluorescence is a technique used for optical microscope, light microscopy with a fluorescence microscope and is used primarily on microbiological samples. This technique uses the specificity of antibodies to their antigen to target fluoresc ...

immunofluorescence
, and fluorescent proteins, such as
green fluorescent protein The green fluorescent protein (GFP) is a protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within orga ...
. These techniques use these different fluorophores for analysis of cell structure at a molecular level in both live and fixed samples. The rise of fluorescence microscopy drove the development of a major modern microscope design, the
confocal microscopeIn geometry, confocal means having the same Focus (geometry), foci: confocal conic sections. * For an optical cavity consisting of two mirrors, confocal means that they share their foci. If they are identical mirrors, their Radius of curvature (opti ...

confocal microscope
. The principle was patented in 1957 by
Marvin Minsky Marvin Lee Minsky (August 9, 1927 – January 24, 2016) was an American cognitive Cognition () refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses many ...

Marvin Minsky
, although
laser A laser is a device that emits light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as h ...

laser
technology limited practical application of the technique. It was not until 1978 when
Thomas Thomas may refer to: People * List of people with given name Thomas * Thomas (name) * Thomas (surname) * Saint Thomas (disambiguation) * Thomas Aquinas (1225–1274) Italian Dominican friar, philosopher, and Doctor of the Church * Thomas the Apo ...
and
Christoph Cremer Christoph Cremer (born in Freiburg im Breisgau, Germany) is a German physicist and emeritus at the Ruprecht-Karls-University Heidelberg, honorary professor at the University of Mainz and was a former group leader at the Institute of Molecular Biolo ...
developed the first practical confocal laser scanning microscope and the technique rapidly gained popularity through the 1980s.


Super resolution microscopes

Much current research (in the early 21st century) on optical microscope techniques is focused on development of
superresolution Super-resolution imaging (SR) is a class of techniques that enhance (increase) the image resolution, resolution of an digital imaging, imaging system. In optical SR the diffraction-limited, diffraction limit of systems is transcended, while in geom ...
analysis of fluorescently labelled samples. Structured illumination can improve resolution by around two to four times and techniques like stimulated emission depletion (STED) microscopy are approaching the resolution of electron microscopes. This occurs because the diffraction limit is occurred from light or excitation, which makes the resolution must be doubled to become super saturated. Stefan Hell was awarded the 2014 Nobel Prize in Chemistry for the development of the STED technique, along with Eric Betzig and William Moerner who adapted fluorescence microscopy for single-molecule visualization.


X-ray microscopes

X-ray microscopes are instruments that use electromagnetic radiation usually in the soft X-ray band to image objects. Technological advances in X-ray lens optics in the early 1970s made the instrument a viable imaging choice. They are often used in tomography (see micro-computed tomography) to produce three dimensional images of objects, including biological materials that have not been chemically fixed. Currently research is being done to improve optics for hard X-rays which have greater penetrating power.


Types

Microscopes can be separated into several different classes. One grouping is based on what interacts with the sample to generate the image, i.e.,
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nan ...

light
or
photons The photon ( el, φῶς, phōs, light) is a type of elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be ele ...
(optical microscopes),
electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one elementary charge. Electrons belong to the first generation (particle physics), generation of the lepton particle family, and are general ...

electron
s (electron microscopes) or a probe (scanning probe microscopes). Alternatively, microscopes can be classified based on whether they analyze the sample via a scanning point (confocal optical microscopes, scanning electron microscopes and scanning probe microscopes) or analyze the sample all at once (wide field optical microscopes and transmission electron microscopes). Wide field optical microscopes and transmission electron microscopes both use the theory of lenses (
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

optics
for light microscopes and
electromagnet An electromagnet is a type of magnet A magnet is a material or object that produces a magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each poin ...

electromagnet
lenses for electron microscopes) in order to magnify the image generated by the passage of a
wave In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular su ...

wave
transmitted through the sample, or reflected by the sample. The waves used are
electromagnetic Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electric charge, electrically charged particles. The electromagnetic force is carried by electromagneti ...

electromagnetic
(in
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine ob ...
s) or
electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one elementary charge. Electrons belong to the first generation (particle physics), generation of the lepton particle family, and are general ...

electron
beams (in
electron microscopes An electron microscope is a microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine objects that are too small to be seen by the naked ...

electron microscopes
).
Resolution Resolution(s) may refer to: Common meanings * Resolution (debate), the statement which is debated in policy debate * Resolution (law), a written motion adopted by a deliberative body * New Year's resolution, a commitment that an individual make ...
in these microscopes is limited by the wavelength of the radiation used to image the sample, where shorter wavelengths allow for a higher resolution. Scanning optical and electron microscopes, like the confocal microscope and scanning electron microscope, use lenses to focus a spot of light or electrons onto the sample then analyze the signals generated by the beam interacting with the sample. The point is then scanned over the sample to analyze a rectangular region. Magnification of the image is achieved by displaying the data from scanning a physically small sample area on a relatively large screen. These microscopes have the same resolution limit as wide field optical, probe, and electron microscopes. Scanning probe microscopes also analyze a single point in the sample and then scan the probe over a rectangular sample region to build up an image. As these microscopes do not use electromagnetic or electron radiation for imaging they are not subject to the same resolution limit as the optical and electron microscopes described above.


Optical

The most common type of microscope (and the first invented) is the
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine ob ...
. This is an
optical Optics is the branch of physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entitie ...

optical
instrument Instrument may refer to: Science and technology * Flight instruments two-seat light airplane. The flight instruments are visible on the left of the instrument panel Flight instruments are the instruments in the cockpit of an aircraft that pro ...

instrument
containing one or more
lenses A lens is a transmissive optics, optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a #Compound lenses, compound lens consists of several simple ...

lenses
producing an enlarged image of a sample placed in the focal plane. Optical microscopes have
refractive In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior throu ...

refractive
glass (occasionally plastic or
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
), to focus light on the eye or on to another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1250x with a theoretical resolution limit of around 0.250 
micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures The International Bureau of Weights and Measures (french: Bureau international des poids et mesures, BIPM) is an intergovernmental orga ...
s or 250 
nanometre file:EM Spectrum Properties edit.svg, 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its derived scales. The nanometre is often used to express dimensions on an atomic scale and mostly in the Mo ...
s. This limits practical magnification to ~1500x. Specialized techniques (e.g., ,
Vertico SMI Vertico spatially modulated illumination (Vertico-SMI) is the fastest light microscope for the 3D analysis of complete cells in the nanometer The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI ...
) may exceed this magnification but the resolution is
diffraction Diffraction refers to various phenomena that occur when a wave In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which r ...

diffraction
limited. The use of shorter wavelengths of light, such as ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the
near-field scanning optical microscope flake using NSOM with a campanile probe (top) and conventional confocal microscopy (bottom). Scale bars: 1 μm. Near-field scanning optical microscopy (NSOM) or scanning near-field optical microscopy (SNOM) is a microscopy technique for nanostruct ...
.
Sarfus Sarfus is an optical quantitative imaging technique based on the association of: *an upright or inverted optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible spect ...
is a recent optical technique that increases the sensitivity of a standard optical microscope to a point where it is possible to directly visualize nanometric films (down to 0.3 nanometre) and isolated nano-objects (down to 2 nm-diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy.
Ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, ...

Ultraviolet
light enables the resolution of microscopic features as well as the imaging of samples that are transparent to the eye.
Near infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natur ...
light can be used to visualize circuitry embedded in bonded silicon devices, since silicon is transparent in this region of wavelengths. In
fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection (physics), reflection, and attenuation or absorption (electromagnetic radiation), absorption, to study the properties ...

fluorescence microscopy
many wavelengths of light ranging from the ultraviolet to the visible can be used to cause samples to
fluoresce light. Fluorescence is the emission of light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defi ...

fluoresce
, which allows viewing by eye or with specifically sensitive cameras.
Phase-contrast microscopy __NOTOC__ Phase-contrast microscopy (PCM) is an optical microscopy Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instrume ...
is an
optical microscopy Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes the ...
illumination technique in which small
phase shifts In physics and mathematics, the phase of a periodic function F of some real number, real variable t (such as time) is an angle-like quantity representing the number of Period (physics), periods spanned by that variable. It is denoted \phi(t) and ex ...
in the light passing through a transparent specimen are converted into amplitude or contrast (vision), contrast changes in the image. The use of phase contrast does not require
staining specimen, sandwiched between a glass microscope slide. Staining is a technique used to enhance contrast in samples, generally at the Microscope, microscopic level. Stains and dyes are frequently used in histology (the study of tissue under the ...
to view the slide. This microscope technique made it possible to study the cell cycle in live cells. The traditional optical microscope has more recently evolved into the digital microscope. In addition to, or instead of, directly viewing the object through the
eyepiece An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as Optical telescope, telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks t ...
s, a type of sensor similar to those used in a digital camera is used to obtain an image, which is then displayed on a computer monitor. These sensors may use CMOS or charge-coupled device (CCD) technology, depending on the application. Digital microscopy with very low light levels to avoid damage to vulnerable biological samples is available using sensitive photon counting, photon-counting digital cameras. It has been demonstrated that a light source providing pairs of Photon entanglement, entangled photons may minimize the risk of damage to the most light-sensitive samples. In this application of ghost imaging to photon-sparse microscopy, the sample is illuminated with infrared photons, each of which is spatially correlated with an entangled partner in the visible band for efficient imaging by a photon-counting camera.


Electron

The two major types of electron microscopes are
transmission electron microscope . The polio virus is 30 nm in diameter. Transmission electron microscopy (TEM) is a microscopy Microscopy is the technical field of using microscope A microscope (from grc, μικρός ''mikrós'' 'small' and ''skopeîn'' 'to look ( ...

transmission electron microscope
s (TEMs) and
scanning electron microscope A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...
s (SEMs). They both have series of electromagnetic and electrostatic lenses to focus a high energy beam of electrons on a sample. In a TEM the electrons pass through the sample, analogous to bright field microscopy, basic optical microscopy. This requires careful sample preparation, since electrons are scattered strongly by most materials. The samples must also be very thin (below 100 nm) in order for the electrons to pass through it. Cross-sections of cells stained with osmium and heavy metals reveal clear organelle membranes and proteins such as ribosomes. With a 0.1 nm level of resolution, detailed views of viruses (20 – 300 nm) and a strand of DNA (2 nm in width) can be obtained. In contrast, the SEM has raster coils to scan the surface of bulk objects with a fine electron beam. Therefore, the specimen do not necessarily need to be sectioned, but coating with a nanometric metal or carbon layer may be needed for nonconductive samples. SEM allows fast surface imaging of samples, possibly in thin water vapor to prevent drying.


Scanning probe

The different types of scanning probe microscopes arise from the many different types of interactions that occur when a small probe is scanned over and interacts with a specimen. These interactions or modes can be recorded or mapped as function of location on the surface to form a characterization map. The three most common types of scanning probe microscopes are atomic force microscopy, atomic force microscopes (AFM), near-field scanning optical microscopy, near-field scanning optical microscopes (MSOM or SNOM, scanning near-field optical microscopy), and scanning tunneling microscopy, scanning tunneling microscopes (STM). An atomic force microscope has a fine probe, usually of silicon or silicon nitride, attached to a cantilever; the probe is scanned over the surface of the sample, and the forces that cause an interaction between the probe and the surface of the sample are measured and mapped. A near-field scanning optical microscope is similar to an AFM but its probe consists of a light source in an optical fiber covered with a tip that has usually an aperture for the light to pass through. The microscope can capture either transmitted or reflected light to measure very localized optical properties of the surface, commonly of a biological specimen. Scanning tunneling microscopes have a metal tip with a single apical atom; the tip is attached to a tube through which a current flows. The tip is scanned over the surface of a conductive sample until a tunneling current flows; the current is kept constant by computer movement of the tip and an image is formed by the recorded movements of the tip.


Other types

Scanning acoustic microscopes use sound waves to measure variations in acoustic impedance. Similar to Sonar in principle, they are used for such jobs as detecting defects in the subsurfaces of materials including those found in integrated circuits. On February 4, 2013, Australian engineers built a "quantum microscope" which provides unparalleled precision.


Mobile apps

Mobile app microscopes can optionally be used as
optical microscope The optical microscope, also referred to as a light microscope, is a type of microscope A microscope (from the grc, μικρός, ''mikrós'', "small" and , ''skopeîn'', "to look" or "see") is a laboratory instrument used to examine ob ...
when the flashlight is activated. However, mobile app microscopes are harder to use due to visual Noise (video), noise, are often limited to 40x, and the resolution limits of the camera lens itself.


See also

* Fluorescence interference contrast microscopy * Laser capture microdissection * Microscope image processing * Microscope slide * Multifocal plane microscopy * Royal Microscopical Society


References


External links


Milestones in Light Microscopy
''Nature Publishing''


Nikon MicroscopyU, tutorials from Nikon


{{Authority control Microbiology equipment Microscopes, Microscopy Scientific instruments Science and technology in the Dutch Republic 1590s in the Dutch Republic 1600s in the Dutch Republic 17th-century introductions