Nanotube. Molecular graphic of a nanotube. Each blue sphere represents a carbon atom. Nanotubes consist of sheets of hexagonally linked carbon atoms wrapped around each other in spiral fashion to form a hollow cylinder with a core up to 15 nanometres wide. They were first 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."