Melatonin receptors are a family of G protein-coupled receptors (GPCRs) comprised of MT1 and MT2 receptors. Melatonin receptors bind the endogenous ligand melatonin, a chemical produced within the pineal gland. Melatonin is responsible for regulating a variety of biological processes, such as reproductive and circadian rhythms, sleep, and hormone production. The MT1 receptor is primarily responsible for the sleep promoting effects of melatonin, while the MT2 receptor’s primary role is in the regulation of circadian rhythm following the natural day-night cycle. MT2 receptors also regulate the function of osteoblasts, and have been found to play a role in type 2 diabetes. Research is being done on the potential application of melatonin in the treatment of neuro-disorders like Alzheimer’s, Parkinson’s, addiction, and depression. Melatonin is already commonly used as remedies for jet lag and insomnia.