Nitric oxide is a natural molecule that has many biological and industrial functions. The molecule is composed of one nitrogen atom and one oxygen atom. It is considered a free radical, meaning it has unpaired valence electrons, making it highly chemically reactive. It is not a very popular molecule because many people know what it is used for, but it has many subtle and important uses. Nitric oxide being a natural molecule, it has existed since the dawn of time. It was first studied by Joseph Priestly, an 18th-century English chemist, who believed nitric oxide was simply a poisonous gas. It was not until 1987 that it was discovered that the molecule was produced naturally in our bodies. In 1998, three scientists won the Nobel Peace Prize for discovering how nitric oxide works as a cell signaling molecule. Nitric oxide has actually been used, in the form of the noni plant, as a cure-all medicine in the Pacific Islands for thousands of years. Only in the past 20 years have scientists gradually discovered the connection between the noni plant and nitric oxide. Many people around the world today use the noni plant as a natural medicine to treat various health problems, including coughs, diabetes, liver diseases and many more. Some people also take nitric oxide support supplements, which contain arginine, an amino acid that works with an enzyme in our body to produce nitric oxide (see "Production"). These supplements aim to promote healthy circulation and deliver oxygen to the muscles. The most important uses of nitric oxide are biological, but it is also used industrially. One of the main biological functions of nitric oxide is its role as a neurotransmitter. It is not the same as traditional neurotransmitters like serotonin or GABA. NO is a gas that is synthesized by NO synthase only when needed. When synthesized, it widens blood vessels, allowing greater blood flow to the parts of the body that need it. Researchers believe that NO is released into the blood vessel walls, where it travels to nearby muscle cells and relaxes them, opening the blood vessel. This is how NO helps protect the liver from ischemic injury, which is when there is a lack of blood flow to the liver, resulting in damaged liver cells. Medically, nitric oxide is administered to newborn patients with pulmonary hypertension.