Metallography is the branch of science dealing with the study of the consititution and structure of metals and alloys, its control through processing, and its influence on properties and behavior. Its original implementation was limited by the resolution of the reflected light microscope used to study specimens. This limitation has been overcome by the development of transmission and scanning electron microscopes (TEM and SEM). The analysis of x-rays generated by the interaction of electron beams with atoms at or near the surface, with wavelength- or energy-dispersive spectrometers (WDS, EDS) with the SEM or the electron microprobe analyzer (EMPA), has added quantitative determination of local compositions, e.g., of intermediate phases, to the deductions based upon observations. Introduction of metrological and stereological methods, and the development of computer-aided image analyzers, permits measurement of microstructural features. Crystallographic data can be obtained using classic x-ray diffraction methods using a diffractometer, or diffraction analysis can be performed with the TEM using selected area or convergent-beam electron diffraction (SAD and CBED) techniques, and more recently with the SEM with the orientation-imaging (EBSD) procedure. There is a wide variety of very sophisticated electron or ion devices that can be utilized to characterize surfaces and interfaces, but these devices are generally restricted in availability due to their high cost.