Nanotechnology is one of the most important research and development frontiers in modern science. It was originally used to define any work done on the molecular scale, or one billionth of a meter (nm or 10–9 m). At nanometer length scale, the properties of a material such as its melting point, its electronic and optical properties will change. Sometimes, the classical theory can not describe some phenomena of the material at atomic level. However, the change of these properties offers new opportunities for technological and commercial development and applications.