LNG or Liquefied Natural Gas.
LNG is Natural Gas cooled down to condensate at -161oC (-258oF).
Natural gas consists primarily of methane. Impurities and heavy hydrocarbons from the gaseous fossil fuel are removed before the cooling process.
The density of LNG is roughly in the range 410 to 500 kg/m3. The volume of the liquid is approximately 1/600 of the gaseous volume at atmospheric conditions.