David Smith believes he has build the world's smallest working train, and based on the images and video I wouldn't doubt that claim. Apparently, it is 35,000 times smaller than the real deal.
Of course, it would have been more legit as a model train if it ran on its own mini engine instead of a rotating external motor, but since nano machines of that caliber are not readily available, I will have to call this build impressive nonetheless. Probably could use a little moisturizer on those hands though. [James River Branch via Engadget]