Ruthenium compounds constitute a versatile class of catalysts for important synthetic transformations in organic chemistry. The ability of ruthenium to access different oxidation states and to accommodate a large variety of ligands in various coordination geometries gives rise to numerous different metal complexes. These characteristics have led to the use of a large variety of ruthenium complexes in diverse types of research areas such as artificial photosynthesis, photomolecular devices, studies on biological macromolecules, catalytic oxidation of water and organic substrates, and organic synthesis. This book presents current research from across the globe in the study of ruthenium across a broad spectrum of topics.