The pineal gland.
D000818:Animals; D001683:Biological Clocks; D002417:Cattle; D002628:Chemoreceptor Cells; D006801:Humans; D008027:Light; D008407:Mast Cells; D008550:Melatonin / Q000096:biosynthesis / Q000378:metabolism; D009362:Neoplasm Metastasis; D010870:Pineal Gland / Q000033:anatomy & histology / Q000166:cytology / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D010871:Pinealoma; D009435:Synaptic Transmission
D008550:Melatonin