Nanotube. Coloured transmission electron micrograph showing the capped end and multi-layer wall of a nanotube. Nanotubes consist of sheets of carbon atoms arranged in hexagons. The sheets are wrapped around each other to form a cylinder with a hollow core up to 15 nanometres (nm) across and 100-200nm long. Nanotubes were discovered during experiments to synthesise buckyballs" - football- shaped molecules of carbon (C60). The tube-shaped molecules, also called buckytubes, could be used to design miniature electrical circuits little bigger than molecules. Scientists have already succeeded in filling nanotubes with metal to make the world's smallest bar magnets."