Publisher Summary This chapter discusses the preface of the book. This thematic volume focuses on “Redox-active Metal Complexes” and is dedicated to the late Dieter Sellmann. The theme of this issue is taken from a collaborative research program, the so-called “Sonderforschungsbereich 583” initiated by Dieter Sellmann and funded by the Deutsche Forschungsgemeinschaft. The present volume includes eight contributions. These contributions cover important advances in inorganic and bioinorganic chemistry with respect to redox-active metal complexes, and trust that the inorganic chemistry community will benefit from them.