I will present some recent results on the scaling limit of disordered systems and some of their consequences. I will mostly focus on the Poland–Scheraga model, also known as the pinning model, which is used to describe DNA denaturation: the question is to know wether (and how) disorder affects its phase transition. I will present some results obtained in a generalized (supposedly more realistic) version of the model, in collaboration with Alexandre Legrand (Université Lyon 1).