Pensieve Header: A coloured tetrahedron for charm and beauty, and to explain how $S_4$ maps onto $S_3$.

{p0, p1, p2, p3} = {{0,0,0}, {0,1,1}, {1,0,1}, {1,1,0}};
tube[a_,b_] := Tube[{a,b}, .1];
ImageCrop@Graphics3D[{
{Red, tube[p0,p1], tube[p2,p3]},
{Green, tube[p0,p2], tube[p1,p3]},
{Blue, tube[p0,p3], tube[p2,p1]}
}, ViewPoint -> {7,6,4},Boxed->False]