One of inventor Chuck Hoberman's expanding structures. By using interlocking folded joints (like fire tongs, with long pieces joined in the middle), the sphere expands from a porcupine looking ball into a large sphere of around 3 times the diameter. This increases the volume of the sphere by close to a factor of 30. For scale it is roughly equivalent to a softball expanding to the size of a basketball. Small versions of these can be bought in almost any science store, and a much larger one graces the entrance to the Liberty Science Center in Jersey City, New Jersey.