Methane (CH4) is one of the most powerful, abundant and surprising greenhouse gases. It is defined in chemistry as a colorless, odorless flammable gas which is the main constituent of natural gas. It is the simplest member of the alkane series of hydrocarbons and is the most commonly found gas. It is a chemical compound that shows up nearly everywhere on the planet. Why and where it shows up is often a mystery. In many ways it is an unknown. The story of methane is a complex and fascinating tale with many current controversies.