High speed video reveals the physics of an ordinary water droplet.

Coalescence is the process by which two(+) droplets merge during contact to form a single one. It’s seen in the formation of raindrops, but also in bigger scales such as planetary and star formation. 

As seen in the video, when the droplet impacts the body of water, a layer of air trapped on the bottom of the droplet prevents it from immediately coalescing, or “collapsing”, into the pool. As this air layer drains away, surface tension pulls some of the droplet’s mass into the pool, while the rest is ejected, bouncing off the surface of the water to repeat the process again. The droplet becomes smaller and smaller until, eventually, the surface tension is able to completely absorb it into the pool.