Time Fountain

This is pretty cool.

This device creates the illusion that a simple stream of water droplets can defy the known laws of physics. By controlling a set of flickering LEDs, the dripping water can appear to slow down, freeze in mid-air, and even reverse in direction.

This illusion exists because the brain attempts to fill in the gaps between flashes with its anticipated motion. It is the same reason that your brain interprets the 24 frames/second of a movie to be in-motion, rather than recognizing the individual still frames.