If you line up two ellipses cut out of paper and tape the edges together, they lie flat. But if you give one ellipse a twist before you connect the edges, the ellipses bow outward to create this 3D form. Tony Wills invented this concept and named the shapes: D-Forms. The photograph above is the result of taping together the edges of two ellipses when one ellipse is rotated 45° with respect to the other. D-Forms aren't restricted to ellipses. You can experiment with any two shapes as long as they have the same perimeter.