With applications in fields as diverse as biology, medicine, geochemistry, metallurgy, solid state physics and archaeology, the high-energy ion microbeam is one of the most versatile of the many research tools currently available to the analytical scientist. The use of focused beams of ions (or 'microprobes') to provide information on the spatial distribution and concentration of chemical elements within a sample is well established (the first working system was developed in the early 1970s), but the enormous potential of the technique has yet to be fully realised. Continuing improvements in microprobe design, coupled with a rapid expansion in the number of operational microbeam facilities around the world, should ensure that the technique fulfils its promise as one of the most exciting new developments in analytical science. This book provides a comprehensive review of the principles and applications of the ion beam technique. The fundamentals of the theory and operation of the microprobe are covered in some depth, but the major portion of the book is devoted to a study of the ways in which the technique has been applied in a wide variety of research fields. The text has been written with the non-specialist in mind, and remains highly readable throughout, while the numerous illustrations and photographs (including an eight-page colour section) lend further clarity to the discussion. For researchers in the many fields of application, or for nuclear physicists interested in applying their expertise in other areas, this volume should be considered essential reading.