Hexagons in nature occur in beehives, on turtle shells, in snowflakes and at the Giant's Causeway. Man-made examples of hexagons include Fort Jefferson, the James Webb Space Telescope and France.
Bees naturally construct honeycombs using hexagonal cells. The theory behind this instinct is that hexagonal cells are more compact than square or triangular cells. Although this theory has existed since Roman times, it was not confirmed mathematically until 1999. Another animal that has a relationship to the hexagon is the tortoise. The center of a tortoise's carapace is usually a line of regular hexagons. However, because the shell is curved, the central hexagons are bounded by pentagons that give a straight edge to the shell.
Snowflakes always form in a hexagonal pattern. This is attributed to hydrogen bonding, which links water molecules in a tetrahedral arrangement. The Giant's Causeway is an area of basalt columns in Northern Ireland; each column has a hexagonal top. The columns' shape is attributed to the irregular cooling pattern of lava following a nearby volcanic eruption.
Fort Jefferson is an unfinished brick fortress built in a hexagonal shape. The fort was built in the Florida Keys. France's borders vaguely resemble a hexagonal shape; French speakers use "l'Hexagone" as a colloquial term for mainland France as opposed to French territories.