- noun a microscope that uses a beam of electrons instead of light.
- A microscope which utilizes a beam of electrons focused by electron lenses to observe and record submicroscopic samples. There are various types, including transmission electron microscopes, which pass an electron beam through a thin sample, and scanning electron microscopes in which the electron beam is scanned over the surface of the specimen. Transmission electron microscopes can achieve resolutions of better than 1 angstrom. For reference, the smallest atom, that of hydrogen, has an approximate width of 1 angstrom. Its abbreviation is EM.