The n-dimensional generalization of a triangle is a n-simplex, the simplest polytope whose faces are all (n-1)-simplices. A 4-simplex is called a 5-cell and is

The n-dimensional generalization of a triangle is a n-simplex, the simplest polytope whose faces are all (n-1)-simplices. A 4-simplex is called a 5-cell and is made of five tetrahedra.