This extremely small unit of temperature measures one billionth of a kelvin (10⁻⁹ K). It is used almost exclusively in ultra-low temperature physics, particularly when studying Bose-Einstein condensates and quantum phenomena near absolute zero. Achieving these temperatures requires advanced laser cooling and magnetic evaporative cooling techniques.
Heard on the job
We managed to cool the rubidium atoms down to about fifty nanokelvin before the magnetic trap failed.