Quantum crystals. Illustration of quantum crystals created by researchers at the Joint Institute for Laboratory Astrophysics (JILA). These quantum crystals were created by precisely overlapping two dense gases of ultracold potassium and rubidium atoms (left) to produce molecules that form an interconnected system (right), in which spin properties can migrate between molecules. Such quantum crystals could lead to the development of new materials. JILA is jointly operated by the University of Colorado Boulder and the National Institute of Standards and Technology (NIST). Image published in 2015.