The venerable muon provides a precision probe for physics of the Standard Model and Beyond. Muon decay determines the strength and structure of the weak interaction, muon capture probes physics not accessible in beta decay, and quantum-loop effects in its anomalous magnetic moment are sensitive to new physics. Recent experimental results from our MuX experiments at PSI elucidate these Standard Model related aspects, whereas the new muon g-2 experiment at Fermilab tries to clarify the persistent discrepancy of more than 3 sigma between experiment and theory, which is suggestive, but not yet definitive, of new physics.