Nitric oxide (NO) is a fascinating and versatile molecule, important for all living things as well as the environment. It is highly reactive and toxic, organisms use it 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). Moreover, NO might have played a fundamental role in the emergence and evolution of life on Earth, as it was available as a high-energy oxidant long before there was oxygen.
