At the end of his December 1959 talk to the American Physical Society, “There’s Plenty of Room at the Bottom”, Feynman offered $1,000 to the first person who could make an operating electric motor the size of a 1/64^th-inch cube. The prize was won the following November by Caltech alumnus William McLellan (left) of Pasadena, who shows it to Feynman for the first time. The “micromotor” was an AC electric motor that weighed 250 micrograms, with output of one millionth of a horsepower. It made the Guinness Book of Records in 1965.

For more on the micromotor and Feynman’s historic talk, see our IN THE NEWS column “The Encyclopedia Britannica on the head of a pin?”