It is increasingly apparent that ion-beam-based processing offers unique capabilities for fabrication and complex patterning of 3D, 2D or 1D structures at the few-nanometer scale (e.g., nanowires and quantum dots), and for custom tailoring of nanocomposites, nanoporous materials, catalyst surfaces, optical materials and nanoparticle assemblies. This book addresses achievements, applications and insights into such areas. It also seeks to identify potential dimensional limitations to the future practical implementation of this approach. Topics include: ion-beam nanofab - tools, techniques and applications; patterning, quantum dot synthesis and self assembly; and examples - applications and devices.