This volume is a continuation of two prior books on advanced electron microscope techniques. The purpose of this series has been to provide in­ depth analyses of methods which are considered to be at the leading edge of electron microscopic research procedures with applications in the biological sciences. The mission of the present volume remains that of a source book for the research practitioner or advanced student, especially one already well versed in basic electron optical methods. It is not meant to provide in­ troductory material, nor can this modest volume hope to cover the entire spectrum of advanced technology now available in electron microscopy. In the past decade, computers have found their way into many research laboratories thanks to the enormous increase in computing power and stor­ age available at a modest cost. The ultrastructural area has also benefited from this expansion in a number of ways which will be illustrated in this volume. Half of the contributions discuss technologies that either directly or indirectly make extensive use of computer methods.