Islets of Langerhans, also called pancreatic islets, are tiny clusters of cells scattered throughout the pancreas. The pancreas is an organ about the size of a hand located behind the lower part of the stomach. Islets of Langerhans contain several types of cells, including beta cells, that produce the hormone insulin. The pancreas also makes enzymes that help the body digest and use food. When the level of blood glucose, also called blood sugar, rises after a meal, the pancreas responds by releasing insulin into the bloodstream. Insulin helps cells throughout the body absorb glucose from the bloodstream and use it for energy. Diabetes develops when the pancreas does not make enough insulin, the body's cells do not use insulin effectively, or both. As a result, glucose builds up in the blood instead of being absorbed by cells in the body.