The proton radius (puzzle?) and its relatives

We review determinations of the electric proton charge radius from a diverse set low-energy observables. explore under which conditions it can be related to Wilson coefficients appropriate effective field theories. This discussion is generalized other constants. provides us with unified framework deal constants associated its electromagnetic interactions. Unambiguous definitions these objects are given, as well their relation expectation values QCD operators. show that obtained spectroscopy and lepton-proton scattering (when both lepton move nonrelativistic velocities) same object underlying theory ${\cal O}(\alpha)$ precision. The model dependence analyses discussed. prospects constructing theories valid for kinematic configuration present, or near-future, experiments