This is amazing. In a little over a minute, you can watch a water droplet on a plate cooled by liquid nitrogen grow first a spike, and then a tiny little forest of ice. The forest spreads across the top of the droplet and grows down the sides. We'll tell you why.
Students from the University of Twente in the Netherlands, grew this miniature forest on top of a water droplet. This is a phenomenon called ice spike, that you can sometimes see in the ice cube trays in your freezer. As the sides of the drop cool, they expand and squeeze the remaining water out the only unfrozen section — in the center of the top. It freezes there, and as more water is pushed out the center, it grows into a spike.
When other water particles in the air build up on that spike — and sometimes on other imperfections of the droplet, they freeze. The parts that stick out catch more little droplets of air, and soon tree-like structures, with branches of ice, build up over the entire surface. Usually, this would take a long time, but because we're seeing it happen on a tiny droplet in a very cold environment, it only takes about five minute in real time, and one minute in time-lapse video. It's an amazing and beautiful process.