Photoinitiating systems for polymerization reactions are largely encountered in a variety of traditional and high-tech sectors, such as radiation curing, (laser) imaging, (micro)electronics, optics, and medicine. This book extensively covers radical and nonradical photoinitiating systems and is divided into four parts: * Basic principles in photopolymerization reactions * Radical photoinitiating systems * Nonradical photoinitiating systems * Reactivity of the photoinitiating system The four parts present the basic concepts of photopolymerization reactions, review all of the available photoinitiating systems and deliver a thorough description of the encountered mechanisms. A large amount of experimental and theoretical data has been collected herein. This book allows the reader to gain a clear understanding by providing a general discussion of the photochemistry and chemistry involved. The most recent and exciting developments, as well as the promising prospects for new applications, are outlined.