Nitric oxide is a fascinating and versatile molecule, important for all living things as well as our environment. It is highly reactive and toxic; it is used as a signaling molecule; it depletes the ozone layer in our planet’s atmosphere; and it is the precursor of the greenhouse gas nitrous oxide (N2O). Nitrogen oxides are also pollutants discharged with exhaust gases, for example from combustion engines in cars, and are harmful to human health.