Differential interference contrast image of a rotifer (Floscularia ringens) feeding. Its rapidly beating cilia (hair-like structures) bring water that contains food to the rotifer. When their cilia beat, the "wheel animacules" first described by Leeuwenhoek (ca.1702) look like two wheels spinning on top. They live in reddish-brown tubes made of spherical "bricks." This image won First Prize, 2011 Olympus BioScapes Digital Imaging Competition®.