Precocious scaling, rescaling, and ξ scaling

All effects of target and constituent masses on the Q2 dependence of lepton-hadron scattering are computable in an expansion in g(Q2), the effective coupling of asymptotic freedom. To leading order, these are summarized by a "best" scaling variable, ξ, which depends on the particular process. The results relevant to low Q2 and charm threshold are discussed.