The gallbladder
The gallbladder is a small, pouch-like organ found underneath the liver. Its main purpose is to store and concentrate bile.
Bile is a liquid produced by the liver to help digest fats. It's passed from the liver into the gallbladder through a series of channels known as bile ducts.
The bile is stored in the gallbladder and, over time, becomes more concentrated, which makes it better at digesting fats.
The gallbladder releases bile into the digestive system when it's needed.