In 1959, physicist Richard Feynman held a talk in which he described a magical future where scientists could shrink computers, medical equipment and all sorts of then-huge things to the size of those mites that live in your eyelashes. Considering that this was an era when computers were the size of a house and ran on whale oil, the predictions sounded somewhat ridiculous. So, Feynman decided to throw down the scientific gauntlet: He bet a cool grand ($8,000 in today's dollars) that nobody could build a working motor that measured no more than 1/64 of an inch on a side. Just so you don't have to break out your ruler, that's about the size of a grain of salt.
About six months passed with no one managing to construct the sweet-ass minuscule motor Feynman had described, despite the prospect of being able to finally afford an awesome new dirt bike. But then along came a guy named Bill McLellan, who -- using such sophisticated scientific equipment as goddamn tweezers and toothpicks -- totally built Feynman's motor. The thing packed 2,000 rpm, weighed 250 micrograms, was smaller than the head of a pin and consisted of 13 parts.
Just big enough to create a buzzing sound in your ear, and just small enough that you'd never find it.