Last August, physicists at NIST's Gaithersburg, Md., headquarters announced that they had cooled cesium atoms to 700 nano-kelvins, or 700 billionths of a degree above absolute zero (minus 273 degrees Celsius, the temperature at which atomic thermal motion would cease). Now, that world record mark for a kinetic (resulting from the thermal motion of atoms) temperature has been bettered by a team at JILA, the Boulder, Colo., institute operated jointly by NIST and the University of Colorado. The scientists, led by physicist Eric Cornell, recently recorded in a gas a much lower kinetic temperature of 200 nanokelvins, or 200 billionths of a degree above absolute zero. They confined a large number of atoms of rubidium in a tiny trap using a magnetic field. The hottest (fastest) atoms then were allowed to escape from the trap, leaving the cooler (slower) ones behind. The process is analogous to the way coffee cools in your cup by evaporation. Eventually, the researchers were left with about 50,000 atoms confined to a region only 23 micrometers on a side, and moving with an average speed of only 4 millimeters per second. They measured the speed by making the atoms fluoresce under infrared laser light, and videotaping the cloud motion through a microscope. From this, Cornell's team could infer the temperature. Potential applications of the technique include improved spectroscopy and metrology in general, and may lead to a better understanding of quantum statistical effects, such as superconductivity.