Electron probe microanalysis developed as a consequence of the successful design and applications of electron microscopy. The principle of x-ray analysis employed in the detection of characteristic x-ray emission from the electron focal zone on a specimen surface mainly derives from the classical x-ray spectroscopy features first exposed by H. Moseley. Many materials exhibit fluorescence in the visible portion of the spectrum both on the incident and emergent side of a thin specimen irradiated by an electron beam. Secondary electrons differ very markedly from backscattered electrons in energy. Depth profile analysis can be coupled with the Auger electron spectrometer system to systematically desorb surface atoms by ion bombardment or high-energy electron bombardment. Perkin-Elmer Physical Electronics Division has developed a commercial scanning Auger microprobe which utilizes a cylindrical-mirror electron energy analyzer with an integral, coaxially mounted electron gun.