One of the most popular puzzle toys in the world, the Rubik's Cube is turning 40. To celebrate the anniversary, its inventor, Hungarian architect Erno Rubik, has teamed up with the Liberty Science Center in Jersey City, New Jersey, for an interactive exhibit. Visitors can admire various cubes from the very first prototype made of wood and rubber bands to the world’s most expensive Rubik’s Cube, made of 18 karat gold and more than a thousand precious stones.