We have some great pictures on the web site of the hail from this morning. But one picture actually shows the inside of hail, as "Mom Clark" from South County sent us a picture with some hail stones cut in half.
If you look closely, especially at that 2nd piece from the left, you'll see rings. Almost like tree rings. That is a clue as to how hail forms. Hail bobs up and down in the updrafts (strong upward moving air that drives those tall storm clouds) and the downdrafts (the downward rush of air from falling rain). Within the storm liquid droplets can become "supercooled" which means it's still liquid but the temperature is below freezing. This happens because the supercooled water droplet needs something to freeze onto. As soon as a piece of hail comes in contact with the supercooled water, it freezes. This creates another layer of ice on the hail. When the hail eventually becomes heavy enough to fall to earth, it will be composed of several layers of ice, like tree rings.
Some of these rings are opaque because they have tiny air bubbles that formed during the freezing process, while the clear color represents the hail going through an area with a lot of supercooled droplets and less air becomes trapped during the freezing. This just illustrates the fact that the hail had several rounds of freezing as it hung up in the thunderstorm.