Nitric oxide is a naturally occurring 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's not a very popular molecule in terms of how many people know what it's for, but it has many subtle and important uses. Since nitric oxide is a naturally occurring molecule, it has been around since the beginning of time. It was first studied by Joseph Priestly, an 18th century English chemist, who believed that nitric oxide was simply a toxic gas. It was only in 1987 that it was discovered that the molecule is produced naturally in our body. In 1998, three scientists won the Nobel Peace Prize for discovering how nitric oxide functions 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 last 20 years have scientists slowly discovered the link between the noni plant and nitric oxide. Many people around the world today use the noni plant as a natural medicine for a variety of health problems, including coughs, diabetes, liver disease, and many others. 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 support healthy circulation and oxygen supply 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. During synthesis, it causes blood vessels to widen, allowing more blood flow to the parts of the body that need it. Researchers believe that NO is released into the walls of blood vessels, where it travels to nearby muscle cells and relaxes them, thus opening the blood vessels. This is how NO helps protect the liver from ischemic damage, which occurs when there is a lack of blood flow to the liver, resulting in damage to liver cells. Medically, nitric oxide is administered to neonatal patients with pulmonary hypertension.