Interferometric scattering microscopy
Interferometric scattering microscopy (iSCAT) refers to a class of methods that detect and image a subwavelength object by interfering the light scattered by it with a reference light field. The underlying physics is shared by other conventional interferometric methods such as phase contrast or differential interference contrast, or reflection interference microscopy.
Source: Wikipedia — Interferometric scattering microscopy (CC BY-SA 4.0)