Cilia--the little hairs that propel a paramecium--flap spontaneously, and will synchronize their movements with neighboring cilia. But exactly why they do this has been hard to pinpoint because cilia are complicated structures; they're comprised of 650 different proteins, says Zvonimir Dogic, of Brandeis University. Reporting in Science, Dogic and colleagues fabricated knockoffs with fewer components to see if they could figure out what drives the waving.