Add to ORKGSimple dynamics, few available decay channels, and highly controlled radiative and loop corrections, make pion and muon decays a sensitive means of exploring details of the underlying symmetries. We review the current status of the rare decays: pi+ → e+ν (pie2), pi+ → e+νγ (pie2γ), pi+ → pi0e+ν (pie3), and µ+ → e+νν̄γ. For the latter we report new preliminary values for the branching ratio B(Eγ> 10 MeV, θeγ> 30◦) = 4.365 (9)stat (42)syst×10−3, and the decay parameter η ̄ = 0.006 (17)stat (18)syst, both in excellent agreement with standard model predictions. We review recent measurements, particularly by the PIBETA and PEN experiments, and near-term prospects for improve-ment. These and other similar precise low energy studies complem...