This book is dedicated to Prof. Dr. rer. nat. Valentin L. Popov, who has become an internationally recognized leading figure in the field of tribology within the past 35 years. He has collaborated with numerous scientists and researchers all over the world. His countless publications cover not only research contributions to classical tribology in mechanical engineering, but also to more modern fields such as nanotribology or biotribology. They include experimental investigations, theoretical approaches, and numerical simulations from the nanoscale to the macroscale. In tribute to the outstanding work of Prof. Popov, this book brings together advanced contributions in the field of tribology written by more than 40 distinguished scientists and researchers.