Photoactive coordination complexes of the transition metal elements have long been of interest, with the last few decades seeing a wealth of studies dedicated to their photophysical properties and excited state behaviour. Light-driven applications for these materials are now being realised, such as light-emitting devices, biological imaging probes, and novel chemotherapy agents. This book focusses on the methods of study and applications of photoactive coordination complexes of the d-block elements. The reader will be introduced to the initial design and fundamental photophysical properties of these molecules, before learning how these molecules have been adapted, developed and utilised within a variety of real-world devices, materials and applications. This book will also provide the reader with a clear vision for the future and the remaining challenges that lie ahead in the further development of light-activated functional materials.