Mercury (latin hydrargyrum = liquid silver) is shiny and silvery and the only metal that is liquid at room temperature. It is known since ancient times, when it was believed to be something magical and a cure. More recently it was and still is used in thermometers and barometers and in amalgams as filling for our teeth. Elemental Mercury and many of its compounds are very toxic, so it should be avoided and not be used, if there are alternatives. Where Mercury is released, it is a big threat for health and environment.