Krypton is a noble gas which means it does not react with many other elements. It is clear and has no taste or smell. The atmosphere is only about one millionth part krypton. The name "kypton" comes from the Greek word "kryptos" meaning hidden. It is used in fluorescent lamps, flashbulbs, and as a wavelength standard. The metre used to be defined as 1,650,763.73 wavelengths in a vacuum of krypton gas. Krypton has very few compounds.