Several years ago, scientists discovered that a single microscopic particle could rock back and forth on its own under a steady electric field. The result was curious, but lonely. Now, Northwestern University engineers have discovered what happens when many of those particles come together. The answer looks less like ordinary physics and more like mystifying, flawlessly timed choreography.

The study appears in the journal Nature Communications.

In the work, the team found that groups of tiny particles suspended in liquid oscillate together, keeping time as though they somehow sense one another’s motion. Nearby particles fall into sync, forming clusters that appear to sway in unison—rocking back and forth with striking coordination.