Abstract
The pineal gland was appreciated as a distinct anatomical entity from antiquity associated with a role in mysticism and in religion as the seat of the soul. The gland appears to have had a photoreceptive role earlier in evolution but typical of vertebrate adaptability it has undergone a role change to a secretory organ with changing needs of the organism. In the contemporary settling it is now known for its neuroendocrine product, melatonin and its association with the sleep cycle. An ancient pleiomorphic molecule with a range of attributes but its antioxidant properties, which helped organisms survive oxygenation of the atmosphere at the dawn of time, is still relevant today, providing an extra layer of protection to the organism as whole but particularly the brain, mitochondria and the skin. Melatonin, through its seasonal influence on the immune function, may also affect disease susceptibility.