Carbon exists in many forms: as the crystalline allotropes graphite and diamond, as amorphous carbon, and as the nanomaterials carbon nanotubes, graphene and Buckminsterfullerene that was named after Buckminster Fuller (1895–1983) and more often called buckyballs or fullerenes. The last three forms are one-dimensional, two-dimensional and three-dimensional nanostructures that were first synthesized in 1991, 2004 and 1985, respectively. The British chemist Harold Kroto (1939–2016) and the two American chemists Robert Curl (1933-) and Richard Smalley (1943–2005) were awarded the 1996 Nobel Prize in Chemistry for their discovery of buckyballs, while two British physicists Andre Geim and Konstantin Novoselov were awarded the 2010 Nobel Prize in Physics for their isolation of graphene. Carbon nanotubes were first synthesized by Japanese researcher Sumio Iijima (1939-). Only graphite, which is found naturally as a gray metallic-looking mineral, is the stable or equilibrium form of carbon.