In 1995, Wolfgang Ketterle and his colleagues have cooled a sodium gas to the lowest temperature ever recorded: only half-a-billionth of a degree above absolute zero, which is -273.15°C (−459.67°F), which is actually unreachable. They managed to achieve this at Ketterle’s lab, MIT, Cambridge. This accomplishment still holds the record according to Guinness World Records for lowest temperature. They bested the previous record by a factor of six, and is the first time that a gas was cooled below 1 nanokelvin (one-billionth of a degree).
In doing so, Ketterle and his team discovered a new form of matter, the Bose-Einstein condensate, where the particles march in lockstep instead of flitting around independently. The discovery of Bose-Einstein condensates was recognized with the 2001 Nobel Prize in physics, which Ketterle shared with his Boulder colleagues Eric Cornell and Carl Wieman.