The flat torus Z(u,v) = (cos(u), sin(u), cos(v), sin(v)) lies on the three-dimensional sphere of radius √2. Stereographic projection from (0,0,0,√2) to the hyperplane of the first three coordinates produces a torus of revolution. Rotating the sphere in the 1,4-plane, gives a one-parameter family of tori, stretching out to infinity and coming back turned inside-out.