Fullerenes are made entirely of carbon. Each carbon forms two single bonds to neighbouring atoms, plus one double bond. The example below is the most famous fullerene, C60.

Geometry: Each carbon is planar trigonal.

The pattern of double bonds is not fixed: Each carbon can form a double bond with any one of the three neighbouring atoms. This allows each sheet of carbon atoms to conduct electricity.

The bonding between the molecules is weak van der Waals' attraction. The molecules can slide past one another which makes fullerenes brittle.

The molecule is hollow. It is possible to create fullerenes with atoms of other elements trapped inside, e.g. a potassium ion.