3D quantum gas atomic clock. This three-dimensional (3-D) quantum gas atomic clock consists of a grid of light formed by three pairs of laser beams. Equipment is used to configure optical components around a vacuum chamber. Shown here are lenses and other optics, with a blue laser beam exciting a cube-shaped cloud of strontium atoms located behind the round window at centre. Strontium atoms fluorescence strongly when excited with blue light. This atomic clock, used for extremely precise time measurements, was developed by researchers at the Joint Institute for Laboratory Astrophysics (JILA). JILA is jointly operated by the University of Colorado Boulder and the National Institute of Standards and Technology (NIST). Image published in 2017.