The correct answer is option 4. The cells in the pancreas that produce insulin are located in the Islets of Langerhans. These islets are small clusters of cells scattered throughout the pancreas. Within the islets, there are different types of cells, including beta cells. Beta cells are responsible for producing and secreting insulin, which is a hormone essential for regulating blood sugar levels. Insulin plays a crucial role in allowing cells in the body to take in glucose from the bloodstream and use it for energy. When there is a deficiency of insulin or the body becomes resistant to its effects, it can lead to the development of diabetes. Other options listed (thymus, estrogen, and corpus epididymis) are not involved in insulin production.