  The low energy behaviour of Quantum Chromodynamics makes unreliable an
expansion in terms of its coupling strength, since nothing guarantees the
convergence of such expansion. To overcomer such difficulty one resorts to
Lattice QCD or Effective Field Theories. In this thesis we compute hadronic
processes at low energies, using Resonance Chiral Lagrangians as the effective
theory of QCD. The processes we study are important background on the search
for Lepton Flavor Violation, Lepton Universality Violation, Lepton Number
Violation, Second Class Currents and study the Hadronic light-by-light
contribution to the Anomalous Magnetic Moment of the muon. All such processes
are of great interest since all of them are to be studied with an increased
precision in the very near future by different experiments.
