Soft materials have exceptional mechanical, optical or functional properties that find applications in many industrial sectors and in society in general. Examples of such systems are colloids, emulsions, polymers, surfactants. These are the building blocks of biological organisms, blood and other cells, DNA, proteins, etc.. This kind of materials is also found in drug delivery systems and consumer products such as shampoo, shaving cream, paint, plastics and foodstuffs. They are called 'Soft' because they flow or deform easily under external forces, which can happen because they are structured on mesoscopic length scales.
These are scales that are large compared to simple molecules, but generally too small for the naked eye to see. The mesoscopic components often spontaneously organize themselves into complex structures with very striking mechanical, optical, or functional properties. The difference with molecular systems is that specific surface interactions play an important role in the creation of the spectacularly large variation in the properties of the systems. This applies to both the mechanical properties as well as the chemical affinity.