Clock comparison measurements in superbly controlled magnetic field environments provide stringent, low-energy tests of the Standard Model (SM) of Particle Physics. The new "Muon g-2" experiment will use a super-conducting magnetic storage ring to compare the Larmor and cyclotron frequencies of muons to extract the muon anomalous magnetic moment with the unprecedented precision of 140 ppb. The Project 8 experiment at the University of Washington aims to probe the absolute neutrino mass scale down to 40meV/c2 by employing the recently demonstrated technique of cyclotron radiation emission spectroscopy to measure the energy spectrum of tritium β−-decay electrons trapped in a preci- sion magnetic field. Both frequency-based experiments will provide new insight about the mass scale of physics beyond the Standard Model. I will discuss both efforts in the context of low-energy, high-precision tests of the SM, which are complementary to highest-energy particle collider experiments.