This book offers a contemporary overview of nanodiffusion, and details the present state of this rapidly growing field. New conceptions of basic aspects of the diffusion processes occurring at the nanoscale are treated, and many useful insights and results concerning diffusion kinetics in various types of technologically important nanomaterials are presented. The latter include: nanomagnetic materials, consisting of a mixture of magnetic nanoparticles in a residual amorphous magnetic matrix; thin films, bi-layers and multilayers for X-ray or neutron mirrors and for magneto-electronic applications such as GMR; and semiconductor nanosystems for many current and future applications.