The Leidenfrost Effect Causes Water Droplets To Climb Hills
Get a surface hot enough, and water will evaporate off of it. But get it even hotter than that—at a temperature higher than water's boiling point—and you'll witness the Leidenfrost effect. The effect occurs when a thin layer of vapor forms between a liquid and a hot surface, essentially levitating the liquid droplets so that they seem to "skitter" swiftly across said surface.
Key Facts In This Video
The Leidenfrost effect was first described in 1756 by Johann Gottlob Leidenfrost, a German doctor. (0:52)
Water droplets experiencing the Leidenfrost effect can self-propel themselves over ridges. (1:30)
See a "Leidenfrost maze" that directs water through walled pathways: (3:14)