2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/228274The present status of Chiral Perturbation Theory (ChPT) in the strong mesonic sector is discussed. A very short introduction to ChPT is followed by an overview of existing two-loop calculations and the determination of the Low-Energy-Constants (LECs). I discuss the case of $η\toπππ$ decays in somewhat more detail and finish by mentioning some recent work on partially quenched ChPT and on the renormalization group in ChPT.15 pagesHigh Energy Physics - Phenomenologytext