MIT's Self-Assembling Robots.

I don't know whether I'm excited about this or scared of it. Either way, it's really pretty incredible.

M-Blocks are a new breed of self-assembling robot currently in development at MIT. Each cube is about an inch and a half across on each face, with a flywheel on the inside and an array of magnets on the outside. By spinning the flywheel at high speeds–up to 20,000 revolutions per minute–the self-contained units can scoot across tables and flip themselves through the air. Once they come close to another block, a clever system of self-aligning magnets attaches them to their partner. Seeing a single cube clamber on top of another isn’t especially impressive. But watch several move at once, with disparate parts moving independently and the larger whole rapidly taking a totally new form, and you can start to see a hazy path towards Optimus Prime.

Watch: MIT's Self-Assembling Robots Offer Whiffs of Optimus Prime | Wired Design | Wired.com