Melatonin is a hormone that is produced by the pineal gland in humans and animals and regulates sleep and wakefulness. Melatonin is also produced in plants where it functions as a first line of defense against oxidative stress. Melatonin is involved in the entrainment (synchronisation) of the circadian rhythms including sleep-wake timing, blood pressure regulation, seasonal reproduction, and many others. BioVision’s melatonin ELISA kit is a competitive ELISA assay for the quantitative measurement of melatonin in serum, plasma and cell culture supernatants. The density of color is proportional to the amount of melatonin captured from the samples.