An electron microscope that builds up its image as a time sequence of points in a manner similar to that employed in television. While the idea of the scanning electron microscope (SEM) dates back to the 1930s, a great deal of the pioneering development of the instrument took place at Cambridge University, England, during the years following World War II. The SEM became commercially available in 1966 and has rapidly taken its place as a useful addition to the battery of electron optical instruments used in both biological and physical research. A part of the attractiveness of the SEM lies in its ability to utilize both analytic and subjective or intuitive channels in attempts to understand the microscopic world.