Islets of Langerhans are groups of cells scattered within the pancreas that secrete insulin, glucagon and somatostatin.
There are three types of cells in these islets - alpha cells make glucagon, beta cells make insulin and delta cells make somatostatin.
In the disease known as Insulin dependent Diabetes Mellitus (IDDM), an autoimmune reaction destroys the beta cells of the Islets of Langerhans and damages the body's ability to produce its own insulin.