Weis pioneered optically pumped alkali-vapour magnetometry (double-resonance, magneto-optical) with applications to biomagnetism and fundamental physics; FRAP is a founding GNOME node. This vapour-phase approach reaches femto-to-picotesla sensitivities complementary to NV-center diamond ensemble quantum sensors (DEER, nano-NMR, T1 relaxometry) that operate near the pT/sqrt(Hz) regime.