Nanotube technology. Computer artwork of four cylindrical fullerenes (carbon nanotubes) of varying size, with the smaller ones nested inside the larger ones. A possible application of such a structure is to have the nanotubes telescope in and out and oscillate at a high frequency, forming a nanoscale radio transmitter. The hexagonal carbon structure of the nanotubes is shown here. Fullerenes are a structural form (allotrope) of carbon. Theoretically, a wide range of molecular shapes can be engineered at the molecular level using fullerenes. Such structures are being investigated for a wide range of technological and medical uses.