Hadronic contributions to the muon anomalous moment
We discuss the hadronic contributions to the muon anomalous magnetic moment. They are dominated by light quark contributions which are constrained by the mechanism of chiral symmetry breaking. Using the leading order result based on $e^+ e^-$ scattering data, we show that the next-to-leading order contributions in the fine structure constant $\alpha$ can be reliably calculated. Extending this idea to the hadronic four-point function we give a prediction for the light-by-light contribution.