How many sides does a hexagon have?

Six, and it is the most useful shape in that family for one reason: it is the only regular polygon above four sides that tiles a flat surface with no gaps. Triangles and squares do too, but of the three the hexagon encloses the most area for the least perimeter - which is why it turns up wherever something is economising on wall.

Bees build in hexagons because wax is expensive. Basalt cracks into hexagonal columns as it cools and contracts, which is what the Giant's Causeway is. Mud dries into hexagonal plates. Snowflakes are six-sided because of the angle at which water molecules bond. In each case nothing is choosing the shape; it is what a system settles into when it is minimising something.

Saturn has one 30,000 kilometres across at its north pole, a standing wave in the atmosphere that has been turning since Voyager photographed it in 1981. Laboratory experiments spinning fluid in a tank produce polygons at the right speeds, which is the leading explanation and still leaves it the strangest hexagon anyone has photographed.