Smallest organisms

The smallest organisms found on Earth can be determined according to various aspects of organism size, including volume, mass, height, length, or genome size.

Given the incomplete nature of scientific knowledge, it is likely that the smallest organism is undiscovered. Furthermore, there is some debate over the definition of life, and what entities qualify as organisms; consequently the smallest known organisms (microrganisms) may be archaea that can be 200 nanometers long.