Soap bubble freezing then shattering in real time, outdoors with an air temperature of minus 15 degrees Celsius (5 F). The thin crystals of dendritic ice spread over the surface of the bubble as the water freezes. These patterns are known as fern frost, due to the resemblance of the crystal pattern to the fronds of a fern. The bubble wall becomes brittle as it freezes, and the air inside it contracts as it cools, and it only takes a puff of air to shatter it. Filmed in St Paul, Minnesota, in winter.