The growth of interest and research activity in X -ray microscopy is reflected in the increasing size and scope of a related series of international conferences, the latest of which (XRM90) was held at King's College London (3-7 September 1990) with over 130 delegates. Previous conferences in Gottingen and Brookhaven resulted in books in the Springer Series in Optical Sciences, and this volume, the proceedings of XRM90, maintains this tradition. Because of the large number of papers their lengths were strictly limited and, while most papers can be directly identified with conference...