Insulin is a hormone that is secreted by the beta cells of the islets of Langerhans. This hormone controls the glucose levels in blood. When the glucose level in the blood rises, the pancreas secrete insulin which triggers the conversion of glucose to glycogen in the liver cells. It also helps promote the uptake and usage of glucose by the muscle cells. Additionally, glucose is also stored as glycogen and fats in the adipose tissue below the skin. In general, insulin is essential to keep the body healthy and control the blood sugar levels. A problem in the functioning of insulin could lead to a common, yet prevalent disease of Diabetes Mellitus.