Beta cells of the pancreas releasing insulin
The pancreas functions as two organs in one: 98% of pancreatic cells are arranged in grapelike clusters that produce digestive enzymes that are released into the small intestine; the other 2% of pancreatic cells, located in regions called islets of Langerhans, function as an endocrine organ and produce hormones such as insulin. Our bodies (and especially our brains) run on glucose, produced by the digestion of carbohydrates. The body's ability to use glucose as its main source of energy depends on insulin. The cells within the islets of Langerhans that produce insulin are called beta cells.