Gallstones are hard deposits that forms in the gallbladder - a small organ located under the liver which is used to store bile – a digestive fluid secreted in the liver. Most people with gallstones never have/show any symptoms. Once they block a bile duct, it will cause severe pain in the abdomen area. Some people develop just one gallstone, while others develop many gallstones at the same time. Also gallstones may vary in size ranging from as small as a grain of sand to as large as golf ball.