A microscope (a device used to magnify small objects) which beams electrons at and through the object of interest instead of light beams. Instead of a glass lens to bend the light, a powerful magnet is used to bend the electron beam. The microscope can only be operated in a vacuum, and biological specimens of interest must first be protected by coating them with a thin metal layer, which also outlines the structural features of the specimen.
This type of microscope provides the greatest resolution of extremely small details available and has been used to see individual atoms in an object or substance.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.