Reactive Cube

The Reactive Cube by Graham Plumb is a visceral screen, a 3d void filled with water. This water is mixed with an oil based compound designed to remain disparate and suspended in the aqueous state. The original cube played with the depth formed from light refraction on the oil's surface, providing 3-dimensional holographic visuals. Later versions of the cube became interactive, responding to the movements and interference caused by users.

http://grahamplumb.com/cube.html