Reading the title I thought this was going to be about the impossibility of decomposing all 3D polyhedra in tetrahedra [1]. As you may know every polygon in 2D

Reading the title I thought this was going to be about the impossibility of decomposing all 3D polyhedra in tetrahedra [1]. As you may know every polygon in 2D can be however decomposed into triangles, but this result doesn't, surprisingly, extend to 3D: [1] https://en.wikipedia.org/wiki/Sch%C3%B6nhardt_polyhedron https://en.wikipedia.org/wiki/Sch%C3%B6nhardt_polyhedron BTW, whether or not a polyhedron is tetrahedralizable is NP-Complete.