2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/121782I discuss the problem of constructing an effective low-energy theory in the vicinity of a resonance or a bound state. The focus is on the example of the $Δ(1232)$, the lightest resonance in the nucleon sector. Recent developments of the chiral effective-field theory in the $Δ$-resonance region are briefly reviewed. I conclude with a comment on the merits of the manifestly covariant formulation of chiral EFT in the baryon sector.12 pages, 7 figs; plenary contribution to Chiral Dynamics 2006High Energy Physics - Phenomenologytext