Following three printings of the First Edition (1978), the publisher has asked for a Second Edition to bring the contents up to date. In doing so the authors aim to show how the newer microscopies are related to the older types with respect to theoretical resolving power (what you pay for) and resolution (what you get). The book is an introduction to students, technicians, technologists, and scientists in biology, medicine, science, and engineering. It should be useful in academic and industrial research, consulting, and forensics; how­ ever, the book is not intended to be encyclopedic. The authors are greatly indebted to the College of Textiles of North Carolina State University at Raleigh for support from the administration there for typing, word processing, stationery, mailing, drafting diagrams, and general assistance. We personally thank Joann Fish for word process­ ing, Teresa M. Langley and Grace Parnell for typing services, Mark Bowen for drawing graphs and diagrams, Chuck Gardner for photographic ser­ vices, Deepak Bhattavahalli for his work with the proofs, and all the other people who have given us their assistance. The authors wish to acknowledge the many valuable suggestions given by Eugene G. Rochow and the significant editorial contributions made by Elizabeth Cook Rochow.