A cross-disciplinary study of the physical properties of complex fluids, solids, and interfaces as a function of their mesoscopic structures, with empasis on nonequilibrium phenomena. The book introduces readers to the methods of non-equilibrium statistical mechanics as applied to complex materials, but always connects theories with experiments. It shows the underlying connections between topics as diverse as critical phenomena in colloidal dynamics, glassy state relaxation and deformation, reinforced polymer composites, molecular level mixing in nanocomposites, and rough surfaces and interfaces. At the same time, each chapter is designed to be independent from the others so that the book can serve as a reference work as well as a text. It is not designed to review all the recent work in mesoscopic physics, which spans many disciplines, but rather attempts to establish a general framework for understanding and developing new materials that can not be designed by the trial and error methods. A familiarity with the basics of statistical mechanics and condensed matter physics is assumed.