The BABAR experiment was designed to investigate “CP violation,” the idea that matter and antimatter behave in slightly different ways, causing the universe to be filled with matter and not antimatter. By observing the collision of high-energy electrons and positrons at SLAC’s B Factory from 1998 through 2008, the BaBar collaboration showed that, indeed, B mesons and their antiparticles do not always decay in the same way, offering strong evidence for CP violation. In 2008, Yoichiro Nambu, Makoto Kobayashi and Toshihide Maskawa were awarded the 2008 Nobel Prize in physics for developing the theory of CP violation.