Above is an example a "smart pebble," outfitted with a microprocessor and magnets, that MIT researchers are using to prototype algorithms for "smart sand" that could form into any shape. Sure, it's early days. But still! Smart sand! From MIT:
At the IEEE International Conference on Robotics and Automation in May — the world's premier robotics conference — (MIT's Distributed Robotics Laboratory) researchers will present a paper describing algorithms that could enable such "smart sand." They also describe experiments in which they tested the algorithms on somewhat larger particles — cubes about 10 millimeters to an edge, with rudimentary microprocessors inside and very unusual magnets on four of their sides.
Unlike many other approaches to reconfigurable robots, smart sand uses a subtractive method, akin to stone carving, rather than an additive method, akin to snapping LEGO blocks together. A heap of smart sand would be analogous to the rough block of stone that a sculptor begins with. The individual grains would pass messages back and forth and selectively attach to each other to form a three-dimensional object; the grains not necessary to build that object would simply fall away. When the object had served its purpose, it would be returned to the heap. Its constituent grains would detach from each other, becoming free to participate in the formation of a new shape.