Microscopes in which a beam of electrons is focused by means of magnetic and electrostatic lenses onto a specimen and scattered by it to produce an image. The resolving power and the magnification of an electron microscope are much greater than can be obtained with an optical icroscope. microscope. The specimen must be examined in a vacuum, which necessitates special techniques for preparing it, and the electrons are usually focused onto a fluorescent screen (for direct viewing) or onto a photographic plate.
