Helium is a colorless, odorless, tasteless, non-toxic an inert gas, and, after hydrogen, is the second lightest and the second most abundant element in the observable universe. On Earth, it is relatively rare, and most is created by the natural radioactive decay of the heavy radioactive elements (thorium and uranium) and is trapped with natural gas in the earth's crust. When released into the atmosphere it quickly escapes into space. It is a non-renewable resource, and its supply is thought to be rapidly diminishing because of its large-scale extraction for industrial applications.