Pancreas
The part of the pancreas that makes hormones is called the Islets of Langerhans. The Islets of Langerhans are a small part (2%) of the total cells in the pancreas.  The Islets of Langerhans change which chemical they make depending on how much of other chemicals are already in the blood.  So, the pancreas works to keep the level of chemicals in balance in the body.  If the Islets of Langerhans stop working, a person will suffer from a disease called diabetes. Doctors are experimenting with taking the Islets of Langerhans cells from a donor body and putting them into the pancreas of a person with diabetes to make that person well.