Colloidal crystals provide scientists with a way to test how atoms interact and what they do during phase transitions. Recent experiments have revealed some surprising things about the nature of these interactions, standing accepted theory on its head. F ar from being exotic laboratory concoctions, colloidal suspensions are found widely in nature. A person sipping a glass of milk is ingesting a colloidal suspension of proteins dispersed in water. Gemstone opals get their fiery colors from crystallized silica colloids that are just the right size for scattering light.
Colloidal systems have many industrial uses as well.
For example, paint consists of pigment particles suspended in a liquid binder. Many of the industrial applications involve controlling the interaction between particles. Materials consisting of linked colloids could have interesting properties. For example, researchers are discussing making photonic crystals, materials that act as semiconductors for light, out of colloids. To do so, they must arrange colloidal particles of a particular size to filter light in a prescribed way.