Exhibit: Graphene

Source: 2009

The hexagonal lattice structure appears in Graphenes, where a single layer of carbon atoms is packed into a two-dimensional honeycomb lattice.

One can also stack different graphene sheets together to graphene layers, a name used as long as the bounding does not define a three dimensional crystal structure. The term graphene should only be used if properties of individual layers are discussd Ref. Related is graphite where the stacking of the hexagonal plane lattices can be different. There are hexagonal or rhombohedral stacking arrangements. The bonds between layers are weak.
Added on September 23, 2011: TPM reports that The MIT-MTL center hopes to be able to syntesize a one-kilometer square sheet of graphene. The hope is to build an industry based on graphene.

Added on March 18, 2012: Scientists create graphene from scratch