A microscopic theory is one that contains an explanation at the atomic or subatomic level in contrast to a higher level or classical macroscopic or ''phenomenological theory''. e.g. in
superconductivity
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...
BCS theory
BCS theory or Bardeen–Cooper–Schrieffer theory (named after John Bardeen, Leon Cooper, and John Robert Schrieffer) is the first microscopic theory of superconductivity since Heike Kamerlingh Onnes's 1911 discovery. The theory describes sup ...
is a microscopic theory.
References
{{atomic-physics-stub
Atomic, molecular, and optical physics