Carbon nanotube. Computer artwork of the inside of a carbon nanotube, also known as a buckytube, showing the hexagonal carbon structure. Atoms are represented as spheres and the bonds between them by rods. Nanotubes are a type of fullerene molecule, a structural form (allotrope) of carbon, whose atoms are arranged into interlinking hexagonal and pentagonal rings. Theoretically, a wide range of shapes can be engineered at the molecular level using fullerenes. Such structures could have a wide range of uses in nanotechnology.