“The cube is a great 3D shape, and it’s so great partly because it’s so regular. In 2D, if you remember, we had our regular polygons which had all angles and edges the same, and now we can extend this to 3D. The 3D equivalent of a polygon is a polyhedron, and it’s made by joining polygons together in the third dimension. A cube is a polyhedron made by joining six square polygons together. A tetrahedron is a polyhedron made from four triangle polygons. Whereas polygons have only corners and edges, a polyhedron also has vertices where the polygon corners meet. A regular polyhedron is one made only from identical regular polygons and in which all the vertices are also exactly the same.”