So basically, gallstones are cholesterol crystals or pigment cells that are little crystals that basically can clump together within the gallbladder and similar to how pearls form in an oyster, get bigger and bigger to form stones. Now you can have two different types of gall stones. One can be cholesterol gall stones or they can be pigment gall stones. The cholesterol gall stones are caused from high fat diets or high cholesterol and the pigment stones are basically from digested blood cells. So there are certain populations of patients that can get one versus the other. People with sickle cell disease or diseases where they have a lot of breakdown of blood can tend to get more pigment stones as opposed to the more common cholesterol gall stones which are formed from high fat diets and poor fiber diets or from obesity. So it's important to understand the difference in the two types of gall stones.