In their quest to build a beating heart from scratch, Harvard University researchers looked to the sea for inspiration, building a tiny swimming “jellyfish” out of rat heart cells and a thin, jellyfish-shaped polymer film.

The real jellyfish, a simple aquatic creature buffeted by ocean currents, may seem a world away from the human heart, but researchers found that the repetitive pulsations jellyfish use to swim through salt water are similar to the way the heart pumps blood through the human body.