BICEP (Background Imaging of Cosmic Extragalactic Polarization) and the Keck Array are a series of cosmic microwave background (CMB) experiments. They aim to measure the polarization of the CMB; in particular, measuring the B-mode of the CMB. The experiments have had three generations of instrumentation, consisting of BICEP1, BICEP2 and the Keck Array, with BICEP3 being constructed . On 17 March 2014, the collaboration announced that BICEP2 had made the first detection of so-called B-mode polarization, a possible signature of inflation in the very early Universe.