For several decades the electron microscope has been the instrument of choice for the examination of biological structures at high resolution. Biologists have be­ come familiar with the techniques and pitfalls of sample preparation and with the interpretation of the images obtained. The purpose of this book is to introduce the biologist to a number of new imaging techniques that are now becoming avail­ able to supplement and even extend the information that can be obtained from the now-traditional electron microscope. Some of these techniques are still at the experimental stage, while others, such as cryoelectron microscopy and confocal optical microscopy, are at advanced stages of development and are already avail­ able commercially. This book represents a first attempt to quantify the progress made by bring­ ing together, in one volume, an account of the technical bases and the future potentials of the various techniques. Although the content is primarily aimed at biologists, microscopists in other fields should also find the information of interest and use. All the chapters are written by leading experts who are at the forefront of these exciting developments. About half the book is concerned with x-ray microscopy; the editors make no apology for this since they are both intimately involved with developments associated with this field and therefore view it, perhaps with bias, as being of the utmost importance.