Use of scanning electron microscopy (SEM) to study chromosomes permits their observation at higher resolution than is possible by light microscopy and, at the same time, provides aesthetically pleasing images. Chromosome preparations made for SEM in the three different ways described in this chapter are illustrated in Fig. 1–3. As can be seen, there is a general resemblance among chromosomes prepared by the three different techniques, but also some differences in detailed structure. At present, it is not possible to say which, if any, bears the closest resemblance to the in vivo state.