A Miniature Origami Robot by MIT and TU Munich researchers:
The unfolded robot, which is made of a magnet and PVC sandwiched between laser-cut structural layers (polystyrene or paper), weighs just 0.31 g and measures 1.7 cm on a side. Once placed on a heating element, the PVC contracts, and where the structural layers have been cut, it creates folds.
Via Technabob.
Check out the video after the break.