Molecules cooled to less than a millionth degree Kelvin above absolute zero can still react chemically with one another despite the temperature causing near-negligible collision motion. “[A new study found that] at just a few hundred nanokelvins above absolute zero, the researchers could even change the speed of the chemical reaction by tweaking the molecules' quantum states, paving the way for highly controlled chemistry using the tools of physics. (A nanokelvin is one billionth of a kelvin.) The study appears in the February 12 issue of Science, authored by scientists from two institutes affiliated with the National Institute of Standards and Technology (NIST): JILA, run jointly by NIST and the University of Colorado at Boulder; and the Joint Quantum Institute, a partnership between NIST and the University of Maryland, College Park. In 2008 a group including many of the same researchers announced the creation of a dense gas of potassium–rubidium (KRb) molecules at a few hundred nanokelvins. Now that ultracold gas has been shown to decay through a heat-releasing chemical reaction as its molecules interact through the phenomenon of quantum tunneling, in which particles skip over classical barriers.”