Emission microscopes and related instruments comprise a specialized class of electron microscopes that have in common an acceleration field in combination with the first stage of imaging (i.e., an immersion objective lens, also called a cathode lens or emission lens). These imaging techniques include photoelectron emission microscopy (PEEM or PEM), electron emission induced by heat, ions, or neutral particles, mirror electron microscopy (MEM), and low-energy electron microscopy (LEEM), among others. In these instruments the specimen is placed on a flat cathode or is the cathode itself. The low-energy electrons that are emitted, reflected, or backscattered from the specimen are first accelerated and then imaged by means of an electron lens system resembling that of a transmission electron microscope. The image is formed in a parallel mode in all of the above instruments, in contrast to the image in scanning electron microscopes, where the information is collected sequentially by scanning the specimen. A brief history and introduction to emission microscopy, MEM, and LEEM is presented as a background for the Proceedings of the Second International Symposium and Workshop on this subject, held in Seattle, Washington, August 16-17, 1990. Current trends in this field gleaned from the presentations at that meeting are discussed.