In 2013, a three-dimensional honeycomb of hexagonally arranged carbon was termed 3D graphene. In compound eyes, the lenses were typically arranged hexagonally. MUO structures are based on a hexagonally close-packed array of oxygen atoms. They were hexagonally shaped and also made of the roughly dressed stone. Using less different block lengths, a "hexagonally packed cylinder" geometry can be obtained. Hex can also be played with paper and pencil on hexagonally ruled graph paper.