The present volume, 44 of Advances in Solid State Physics, contains the written versions of most of the plenary and invited lectures of the Spring Meeting of the Condensed Matter Physics section of the Deutsche Physikalische Gesellschaft held from March 8 to 12, 2004 in Regensburg, Germany. Many of the topical talks given at the numerous and very lively symposia are also included. They covered an extremely interesting selection of timely subjects. Thus the book truly reflects the status of the field of solid state physics in 2004, and explains its attractiveness, not only in Germany but also internationally.