This book presents some of the most recent advances in the theory of chemical processes in the condensed phase. The approaches and applications studied in the book vary widely from classical mechanics to quantum mechanics, encompassing a range of systems from atom transfer reactions in simple fluids to charge transfer in water to biological systems. Each chapter presents an overview of a state-of-the-art technique by investigators who have been at the forefront of developing the approaches. The theoretical study of condensed phase chemistry is one of the most exciting and rapidly expanding fields of chemical physics, and this volume provides a snapshot of the forefront of research in this area.