Book excerpt: Recent extensive activity on severe plastic deformation (SPD) as a new materials processing technology has generated vast experimental and analytical amounts of information. However, there is still a strong need for a multidisciplinary understanding of SPD. This book consists of in-depth analyses of the fundamentals and engineering of SPD on processing mechanics, the micro-mechanics of plastic deformation and the physics of the structure-properties relationship. This book bridges the gap between existing approaches, resolves certain controversies, and provides a united description of SPD at different scales.