This is a milk drop collision. This happens when a drop of milk enters a cup of milk, the drop then rebounds upwards and collides with another drop coming down. The timing for these is critical and I use a kit called SplashArt.
This all happens far too fast for even a camera so the shot is taken in near darkness, the kits fires a few speedlights to capture the action, its about 1/10,000th of a second.
From How do you do that?