Morphine is a natural opioid alkaloid isolated from raw opium in 1805. It has analgesic, anesthetic and other medical uses. Morphine's structure consists of five rings, three in one plane and two perpendicular rings including the nitrogen-containing ring. The phenol and alcohol functional groups, as well as the stereochemistry and nitrogen substitution, are important for morphine's binding and activity. Modifications like acetylation can increase lipid solubility and potency but also toxicity. Replacing the N-methyl group creates the morphine antagonist nalorphine. Morphine's chemical properties underlie its medical uses and abuse potential.