Melatonin (N-acetyl-5-methoxytryptamine) is a tryptophan derived indolic compound. Because of its widespread presences, conserved structure and diverse action it is been considered as new master regulator in living beings. In plants melatonin is establishing itself as new signaling molecule and plant growth regulator. It controls diverse function and physiological processes such as circadian rhythm, seed germination, tropic responses, growth promotion, rooting induction, cellular and cytoskeleton development, reproduction, abiotic and biotic stress protection and senescence regulation. Here in this article we have discussed about the discovery of molecule, its biosynthesis and role in plants with special emphasis on its role under as stress protectant.