Carbon nanotubes are composed of carbon atoms in a honeycomb pattern. They were first discovered by Sumio Iijima in 1991, at that time a researcher at the NEC Tsukuba Research Laboratories. Their diameter is several nanometers, about 1/10,000th the thickness of a strand of human hair. There are two types of carbon nanotubes, single wall nanotubes in which the tube is a single layer, and multi-wall nanotubes made of multiple concentric tubes. Light and extremely strong, carbon nanotubes are gaining worldwide attention.