In the study, published in Nature, researchers used high-speed video to find out what was happening. Drops of liquid usually form tight spheres, but as two electrically charged droplets come close to each other, the spheres begin to warp — and at very short distances, a small bridge of fluid forms between the drops. When the electrical charge is low, that bridge grows until the drops merge together, but when the charge is high, something else happens: the bridge allows the droplets to exchange their charge and then snaps. The water flows back into the bubbles, and by the time the two drops collide, they are back in their spherical shape. Rather than merging, their surface tension causes them to bounce off one another like beach balls [Nature].