"The problem with true three dimensional displays (displays that you can walk around) is that they require pixels to be floating in space. This has been done with lasers and plasma, but such technologies are super expensive and limited in many ways. MIT’s SENSEable City Laboratory in collaboration with ARES Lab (Aerospace Robotics and Embedded Systems Laboratory) has hit upon the idea of creating huge free form three dimensional displays out of individual “smart pixels” made up of micro helicopters carrying LEDs:" - Kurt Starnes