General view of a RCA Model EMU electron microscope used in the Naval Air Material Center's Aeronautical Materials Laboratory. Electron microscopes use a beam of accelerated electrons as a source of illumination and have a higher resolving power that, in contrast to light microscopes, can reveal the structure of smaller objects. Notably, the Model EMU debuted in 1944 and was the first American-manufactured RCA electron microscope capable of both imaging and electron diffraction.