Deep connections are emerging in the physics of non-thermal systems, such as granular media, and other "complex systems" such as glass formers, spin glasses, colloids or gels. This book discusses the unifying physical theories, developed in recent years, for the description of these systems. The special focus of the book is on recent important developments in the formulation of a Statistical Mechanics approach to granular media and the description of out-of-equilibrium dynamics, such as "jamming" phenomena, ubiquitous in these "complex systems." The book collects contributions from leading...