There have been considerable advances in recent times in understanding many common material processes that are of practical importance, such as nonlinear response, fracture, breakdown, earthquakes, packing and granular flow. This has been mainly due to new applications of statistical physics, including percolation theory, fractal concepts and self-organized criticality. This collection of articles brings together research in those closely allied fields. It deals with problems in materials science involving random geometries and nonlinearity at a mesoscopic scale, and problems where randomness in time evolution is as crucial as the geometry itself.