<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> Nitric oxide (nitrogen oxide or nitrogen monoxide), a chemical compound, is a colorless gas under standard conditions, and is one of several oxides of nitrogen . Nitric oxide is a free radical, i.e., its bonding structure includes an unpaired electron, denoted by a dot in its chemical formula, N O. Nitric oxide is also a heteronuclear diatomic molecule, a historic class that drew researches which spawned early modern theories of chemical bonding . </P> <P> A particularly important intermediate in the chemical industry, nitric oxide forms in mixtures of nitrogen and oxygen at high temperatures, as found in combustion systems such as internal - combustion piston engines, gas turbines, furnaces, and boilers . Likewise, nitric oxide forms naturally along the pathway of lightning in thunderstorms . </P>

Where does nitric oxide come from in the body