Courtesy from digg, check out this article with video dramatically demonstrating the freezing of supercooled water.

If you ask most people with the freezing point of water is, they will confidently answer that water freezes at 0 degrees Celsius (or 32 degrees Fahrenheit if you are in a backward country that never shifted to the metric system). But what many people don’t know is that water can exist in liquid form at temperatures which are significantly lower than that. I first remember reading about this in Craig Bohren’s excellent book Clouds in a Glass of Beer: Simple Experiments in Atmospheric Physics. It’s a great book detailing many of the processes that govern weather. He mentions an experiment where you place a small plate with several individual drops of water on a plate and place it in your fridge. You will find that many remain in liquid form for a considerable period of time, and that mechanical jostling of them can cause them to instantly freeze. The video on the webpage above demonstrates some of the same ideas, but much more dramatically.

Cool stuff with a nice writeup.