Nitric oxide was discovered as a secondary messenger in the 1980s and has grown in popularity since that time. In fact, it was named molecule of the year in 1992 by Science Magazine, one of the leading global scientific publications, and the Nobel Prize in Physiology and Medicine for 1998 was awarded to the scientists who discovered its properties as a signaling molecule. Add to that the link to Viagra, one of the most profitable sexual enhancement drugs on the market, and you have a molecular superstar.