Fullerenes are allotropes of carbon consisting of hollow cages made of pentagonal and hexagonal rings. C60 buckminsterfullerene is the most famous fullerene, consisting of 60 carbon atoms arranged in 20 hexagons and 12 pentagons. Fullerenes were discovered in 1985 and have a variety of applications including use as antioxidants, in drug delivery, hydrogen storage, and more. They can form complexes with metals and be intercalated with other elements.