Graphene is the two-dimensional crystalline form of carbon: a single layer of carbon atoms arranged in hexagons, like a sheet of chicken wire with an atom at each nexus. As free-standing objects, such two-dimensional crystals were believed impossible to create — even to exist — until physicists at the University of Manchester actually made graphene in 2004.
http://www2.lbl.gov/Science-Articles/Archive/ALS-graphene.html