The proceedings reflect the Twelfth International Conference on Defects in Insulating Materials, covering topics on point defects and extended defects including theory and computer simulation in various insulating materials, as well as applications in laser physics, imaging, data storage and radioactive waste disposal.

The 1992 International Conference on Defects in Insulating Materials, held in the historical palace of Nordkirchen in Germany, continues a series of successful international conferences. The series developed from a conference on color centers in alkali halides (1956) into the International Conference on defects in Insulating Crystals (ICDIC), 1988 held in Italy. The conference series is merged with the Europhysical Topical Conference on Lattice Defects in Ionic Materials (LATDIM), creating a biannual series of international conferences on this topic. As seen from this year's conference title, the emphasis has proceeded further towards materials science and consequently the conference is now called International Conference on Defects in Insulating Materials (ICDIM). The aim is to provide a forum to bring together scientists from academic research and industry to discuss both the basic physics of defects in a wide range of insulating materials and their role in numerous applications, a rapidly expanding field.

With this book, we wish to honor the lifework of K. Alex Müller and present him with this book on the occasion of his 94th birthday. We are convinced that he will very much enjoy reading it. We would like to thank all contributors to this book, who addressed topics complementary and related to his work. The articles of the book represent the efforts in solid state physics – spanning more than 60 years – which have been groundbreaking in scientific and applied sciences. Many of the current hot topics are derived from this earlier work which has pioneered the way toward new experimental tools and/or refined techniques. From this point of view, the book presents, on one hand, a historical review and, on the other hand, a directory of possible future research.