In every day life many types of granular materials can be found.
Examples are coffee-powder, grains, and sand on the beach or in deserts.
Storage, transport, and handling of granular matter is of eminent industrial importance. The theoretical description and the understanding of the basic phenomena in granular matter is however not yet satisfactory. Due to friction, elastic vibrations, and plastic deformation, energy is dissipated, so that a system of granular particles is not in equilibrium and, consequently, standard methods of statistical physics cannot be applied. Continuum models do not generally work either, since the discreteness of the system is often important. This is a difference to classical gases or fluids where systems of partial differential equations suffice to describe the behavior properly.