This book describes the principles of operation of each type of microscope currently available and of use to biomedical and materials scientists. It explains the mechanisms of image formation, contrast and its enhancement, and accounts for ultimate limits on the size of observable details (resolving power and resolution). Finally it provides an account of Fourier optical theory. Principles behind the photographic methods used in microscopy are also described and there is some discussion of image processing methods. Throughout, the text emphasizes the underlying similarity of all microscope systems and, recognizing that biologists may often be uncomfortable with mathematical approaches every effort has been made to present concepts verbally.