This book provides a cross-disciplinary introduction to the physical properties of complex materials, considered as a function of their mesoscopic structures, with emphasis on nonequilibrium phenomena. Using statistical dynamics as the most suitable framework for describing the behavior of complex fluids, solids, and interfaces, the book establishes a general framework for developing new materials that can not be designed by trial-and-error methods and for understanding their properties. It introduces readers to the methods of nonequilibrium statistical mechanics, but always connects theories with experiments. The treatment shows the underlying connections between topics as diverse as critical phenomena in colloidal dynamics, glassystate relaxation and deformation, reinforced polymer composites, molecular-level mixing in nanocomposites, and microscopic interactions in rough surfaces and interfaces. Rather than reviewing all the recent work in mesoscopic physics, this book is designed to provide an introduction to this broadly interdisciplinary field of research ; each chapter is as independent as possible from the others so that the book can serve as a reference work as well as a text. A familiarity with the basics of statistical mechanics and condensed-matter physics is assumed. The book will be useful as a reference for graduate students and researchers in academia and industry in condensed-matter physics, polymer physics, colloid and interface science, and materials science and engineering.