We now know that neutrinos have mass, and that their weak eigenstates mix. However, the pattern of lepton masses and mixing angles is entirely different from that for quarks. For example, the first and second
generations are almost completely mixed, as are the second and third. The first and third generations, though, have a mixing angle that is consistent with zero, based on existing measurements.

I will briefly review the status of neutrino oscillation measurements and summarize our current knowledge of masses and mixing angles. I will then describe a China/US collaboration mounting an experiment at the Daya Bay
nuclear reactor complex, north of Hong Kong. Our goal is to either measure, or set a limit on, the "last" neutrino mixing angle "θ₁₃ " at a level of 1%.