Fullerenes are molecular cages consisting of only carbon atoms.
The arrangement of the atoms is almost exclusively in the form of hexagons and pentagons. 12 pentagons and 20 hexagons make the most famous C60 cage . This cage was first identified experimentally by H.W. Kroto, R.E. Smalley, and R.F. Curl in 1985 . C60 fullerenes are the most stable and the most abundant species. C60 crystals exhibit several interesting phase transitions and they are photophysically active in several ways.