While they might look like drops of water or soap bubbles, these colorful figures are actually photomultiplier tubes that line the walls of the Daya Bay neutrino detector. Neutrinos and antineutrinos are neutral particles produced in nuclear beta decay when neutrons turn into protons. This experiment aims to measure the final unknown mixing angle that describes how neutrinos oscillate. The tubes are designed to amplify and record the faint flashes of light that signify an antineutrino interaction. Lawrence Berkeley and Brookhaven National Labs and a number of physicists at U.S. universities played leading roles in the Daya Bay experiment, from designing the detectors all the way through to analyzing the data gathered. | Photo by Roy Kaltschmidt, LBNL.