The Leidenfrost Maze, designed and built by Carmen Cheng and Matthew Guy at the University of Bath, demonstrates how Leidenfrost droplets can be self-propelled in a controlled way by the jagged texture of the hot surface.
The basic idea is, when a liquid comes in contact with something really hot—about twice as hot as the liquid’s boiling point, although it changes on certain factors like the size of the drop—the liquid never comes in direct contact with the surface; vapor acts as a barrier that keeps the two separated. When you flick drops of water on to a pan to check the heat, that skittering you see and hear is because of this effect.
Cheng and Guy made the aluminum block maze to inspire and share science with local school kids, though we’re guessing every school around the world would love a physics demonstration kit like this.
There are more excellent physics videos in the archives.