Thin films are used in virtually every manufacturing and technological area. A large fraction of these films are polycrystalline. Their uses range from critical components in the microelectronics industry, to hard coatings for wear resistance, corrosion resistance and thermal barriers, to magnetic, optical and medical applications. It is essential to the functional properties of these films that the microstructure, composition, architecture and stress state be produced with a high level of control which demands a detailed understanding of the mechanisms which are responsible for the formation of structure in polycrystalline thin films. This book focuses on thin polycrystalline metallic, ceramic and semiconducting films of thicknesses in the range of tens to thousands of nanometers. Topics range from fundamental to technological. Topics include: evolution of texture and microstructure; grain boundaries and interfaces; microstructure, stress and texture; characterization and representation; microstructure, texture and reliability; processing, characterization and application and polycrystalline Si and SiGe films.