A gallbladder attack happens when the liquid in the gallbladder crystallizes and it's similar to sugar candy. It's supersaturated with different substances, the most common being cholesterol, and it can actually crystallize and form a stone. Now, the gallbladder again is like a water balloon. It wants to empty after you eat every meal and if it receives a message from the stomach that there is food, it squeezes and it pushes all of the liquid out. If there's a stone in there, the stone may block the opening and the gallbladder will continue to squeeze but it won't empty because the gallstone is actually blocking the opening. The gallbladder doesn't know that. It continues to squeeze, harder and harder and harder and that's what gives us a gallbladder attack.