This monograph, which is the outcome of the ASI on High Pressure Chemistry, Biochemistry, and Materials Science, illustrates new developments in the field of high pressure science. In fact, for chemists, biochemists, and materials scientists, pressure as an experimental variable represents a tool which provides unique information about systems of materials studied. It is interesting to note how the growth of the high pressure field is also reflected in the content of the recent ASI's dealing with this field. The ASI High Pressure Chemistry held in 1977 was followed by the ASI High Pressure Chemistry and Biochemistry held in 1986, and the coverage of the present ASI also includes applications to materials science. In view of the teaching character of the ASI, it is natural that main contributions to this volume present overviews of the different subfields or applications of high pressure research. In contrast, contributed papers offer more specialized aspects of various high pressure studies. The various contributions to this volume make clear the impressive range of fundamental and applied problems that can be studied by high pressure techniques, and also point towards a major growth of high pressure science and technology in the near future. This ASI focused mainly on advances achieved in the six years since the previous ASI devoted to the high pressure field. The organization of this volume is as follows.