Raak: [Blob, rab] The tetrahedron generalises to all dimensions, and is generally known as the n-dimensional simplex. It has n vertexes and n faces, each of which is an n-1-dimensional simplex. The cube and the octahedron also generalise to all dimensions, being known as the hypercube (in 4 dimensions, tesseract), and the cross-polytope. The icosahedron and dodecahedron don't generalise. In four dimensions you get a few other regular polyhedra, such as the one made of 600 tetrahedra.