The official groundbreaking for the planned Mu2e experiment happened a few days ago. I was at Fermilab for unrelated reasons, so I saw the site but didn’t attend the ceremony. Mu2e is one of the experiments planned as part of the “intensity frontier” of the Department of Energy’s general plan for high energy physics experiments. Mu2e will look for muon conversion to electrons with no neutrinos. This violates lepton flavor conservation, which is part of the Standard Model but isn’t required in a more general theory. We know that this process must be very rare, but trying to measure it could help constrain theories of physics beyond the Standard Model.