Nanotube technology. Computer artwork of a cylinder and a tubular ring (torus) made from carbon. The molecular models show the hexagonal carbon structure found in fullerenes, a structural form (allotrope) of carbon. Carbon nanotubes are cylindrical forms of fullerenes, as opposed to the spherical forms, but theoretically a wide range of molecular shapes can be engineered at the molecular level using fullerenes, such as the torus seen here. Such structures could have a wide range of technological and medical uses.