Apart from being able to study and manipulate individual objects, most prominent in the nanotechnology, in many cases the collective behaviour of many individual objects is a challenging field of study as well. Examples are the behaviour of granular material, selfassembly, fracture in materials and problems in hydrodynamics. In a combination of numerical methods with the development of new concepts many new experiments have appeared. Many of those problems are directly related to major engineering disciplines and some arise directly in an industrial context, most notably with (bio-)polymers.