The little hailstone is thrown up inside the cloud, still collecting other cold drops. The hailstone gets bigger and bigger until it goes to the top of the cloud. Then, because there is no more wind, it falls back down through the cloud. While it is falling it gets even bigger as it bangs into more supercooled drops. If it goes down very fast it can hit the earth at up to 90 mph (144 kph), bouncing like popcorn. If the hailstone hits dirt, it can actually bury itself.