The properties of materials and devices are frequently dominated by defects and interfaces. The density, structures and properties of defects and interfaces in crystals must, therefore, be understood and controlled, especially in high performance materials. This book provides the fundamentals on several important issues: how crystal defects are introduced (or avoided) by specific processing routes, how to determine the nature of the defects resulting from processing, and how the specific defects affect certain critical properties. Point, line, and planar defects in solids (mostly crystalline) are covered, with emphasis on fundamentals of structure, energetics, and kinetics, including initial development of most materials behaviour and processing.