EM (electron microscope): A microscope in which an electron beam replaces light to form the image. Electron microscope stands for electron microscope (the device) and for electron microscopy (the technique and field).
Electron microscope generally offers greater magnification and resolution of objects.
Electron microscope was invented by a team led by Vladimir Zworykin, an engineer at the RCA Laboratory in Camden, New Jersey. The device was publicly unveiled in 1940.
The Belgian-born biochemist Albert Claude (1899-1983) was the first person to examine cells under electron microscope and see a cancer-associated virus (thanks to electron microscope). Much of his research was performed at the Rockefeller Institute (now the Rockefeller University) in New York and in 1974 shared the Nobel Prize in Physiology or Medicine with Christian De Duve and George Palade for "their discoveries concerning the structural and functional organization of the cell."