To understand, at a microscopic level, the properties of different materials, thus allowing the desing of new materials with specific microstructured properties that could be useful in many applications (soft materials, gels, glasses, polymeric systems and complex liquids). A good example of this is water, which, in contrast to normal liquids, expands when cooled in the range 0 and 4ºC and whose molecules move more quickly at higher density in a certain pressure range. In this respect, amongst other aspects, the underlying microscopic causes of this behaviour are studied