World's Smallest Electric Motor / Generator.

These two micro DC motors, is the smallest I can find for sale on the Internet, only 3.1 x 8 mm. Runs more than 100,000 Rpm at 5 to 7 volts.

You can find them here. 1pcs $1. SANYO Micro Coreless DC motor.

http://www.ebay.com/itm/181971305218?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT