This handbook contains accounts of state-of-the-art approaches to the physics of granular matter, from a widely interdisciplinary and international set of experts in the field. The authors include theorists such as S.F. Edwards, J. Krug and J. Kurchan, and they seek to report current experimental approaches with, importantly, a detailed account of new techniques. The volume should serve as a useful manual for all researchers, both novice and experienced, who wish to get quickly directed to open questions in key aspects of this challenging and topical domain.