Up to about twenty-five years ago, virtually the entire field of microscopy could be overseen and even practized by any active research worker. The rapid evolution which microscopy in its broadest sense has since undergone and which has contributed greatly to our insight in many fields of biological science and medicine has, however, lead to a progressive specialisation. Both experienced investigators in clinical and biological laboratories and post­ graduate students, confronted with a limited number of microscopic tech­ niques in their daily research work, have increasing difficulty in keeping (or obtaining) a general idea of the many time-honoured and new possibilities which microscopy has to offer. This book has been written with the aim of presenting general informa­ tion on light microscopic techniques, at a level somewhere in between booklets like those provided by microscope manufacturers (which are often too much focussed on the production program of a particular make) and very advanced treatises with a thorough mathematical treatment of all phenomena concerned. The physically oriented texts moreover often do not sufficiently take into account the practical situation in a medical or biolog­ ical laboratory; on the other hand, the value of really understanding what one is doing in using a microscopic technique is often underestimated. At­ tempt has been made, therefore, to present sufficient background informa­ tion necessary for a rational application of the different microscopical tech­ niques in their mutual relationship.