Sonobe modules follow the rules of traditional modular origami, beginning with a flat square of paper and then combining pieces into structures without tape or glue. The cube that you can make from this simple start is particularly elegant and appealing. It is the same on all six sides and very stable, and it can be combined to make other structures.
Four Sonobe blocks make a bigger cube, but why stop there? They also form the building blocks of what is called a Soma cube, which was invented in the early 1930s by Piet Hein, a Danish mathematician who invented many other games and puzzles. (Hein is said to have come up with the idea during a lecture on quantum mechanics conducted by the physicist Werner Heisenberg, though the timing has been disputed.)
Making a Soma cube requires folding 27 Sonobe cubes, then combining them in groups of either three or four into seven pieces. The pieces are then assembled into a three-by-three-by three cube. There are 240 ways to put the pieces together to form a Soma cube — challenge yourself or a friend to find as many as you can.