The thymus gland is a small organ located in the upper chest, just behind the sternum. It plays a crucial role in the immune system, particularly during childhood and adolescence. The thymus is responsible for the maturation of T-cells, a type of white blood cell that helps the body fight infections and diseases. As a person ages, the thymus gradually shrinks and becomes less active, a process known as thymic involution. Despite its reduced size, the thymus remains important for maintaining immune function. The gland is most active during the early years of life, contributing significantly to the development of a robust immune system.