Insulin is a hormone that regulates blood sugar levels, and it is secreted by beta cells. Beta cells are found in the pancreas, specifically in clusters called islets of Langerhans. These cells play a crucial role in maintaining glucose homeostasis in the body. When blood sugar levels are high, beta cells release insulin, which allows cells to take in glucose from the blood and use it for energy production. This helps to lower blood sugar levels. If beta cells are not functioning properly, it can lead to the development of diabetes mellitus. It is important to note that alpha cells, delta cells, and nerve cells do not secrete insulin. Alpha cells produce glucagon, which is responsible for raising blood sugar levels, while delta cells produce somatostatin, which regulates insulin and glucagon secretion.