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, that are of immense practical importance. 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 material science involving random geometries and nonlinearity at a mesoscopic scale, where local disorder and nonlinearity influence the global behaviour of cracks, for example, and problems where randomness in time evolution is as crucial as the geometry itself.