The information presented in this chapter clearly shows the usefulness of SEM for analyzing the components of the wall of microvessels. The literature contains several methodologies that allow one to successfully expose single smooth muscle cells that line microvessels. It appears that chemical and enzymatic digestion steps will continue to be the principal elements of any methodology for exposing these cells. The combination of microdissection, prior to processing the specimen for SEM, with digestion has allowed better preservation of the tissues by reducing the amount of material obscuring the tissue of interest as well as reducing the length of time the tissue is exposed to chemicals. The next important improvement was the mobilization step of selected vessel segments so that they could be mounted "end on" for circumferential viewing and photographing. Finally, at least three different mathematical approaches have been developed and tested for the quantitation of single cell length and width determination.