In the relatively short time since it has been developed, the scanning electron microscope has proven itself to be an instrument capable of aiding in the solution of a broad spectrum of engineering problems. This has come about because of the unique characteristics of this instrument. The theory of operation of the scanning electron microscope will be given. The manner of image formation and display will be discussed. The operating parameters of the instrument will be given. The types of specimens which may be viewed will be considered along with special sample preparation procedures which mustbe used for different materials. The different modes of operation of the scanning electron microscope will be discussed. These will include secondary electron, backscattered electron, absorbed electron, transmitted electron, cathodoluminescence, and voltage contrast techniques. Means for obtaining compositional information about the specimen will be considered. Special instrumentation to increase the versatility of the work which can be done will be mentioned. Examples illustrating the different modes of operation of the instrument as well as the types of problems which can be handled will be given.