In 1958, when Aaron Lerner isolated and characterised melatonin from bovine pineal tissue, he hoped it would be a treatment for vitiligo – a disease which causes loss of skin colour. When this was proven not to be the case, Lerner almost abandoned research on the molecule. Since then, however, due to the efforts of a troop of inquisitive scientists, a bewildering array of functions have been ascribed to this bewitching molecule. Melatonin predictably evolved several billion years ago in the earliest life forms, bacteria, for protection against toxic chemically reduced oxygen species. Since its creation, melatonin seems to have been preserved in every living organism, both animal and plant. During its long evolutionary history, melatonin has insinuated itself into many aspects of organ and organismal physiology to the extent that its “fingerprints” are all over subcellular infrastructure. Indeed, it seems possible that cells cannot maintain a healthy lifestyle if melatonin is not present. As melatonin has been loitering in cells for a very long evolutionary period, it also has taken advantage of the opportunities to “learn” to functionally cooperate with other beneficial molecules. Subsequently, one feature that characterises melatonin’s actions is diversification.