abstract: I will report on a joint work with Ilaria Mondello (Paris XII) and David Tewodrose (Nantes). We study Gromov-Hausdorff limits of Riemannian manifolds whose Ricci curvature satisfy some Kato bound. This condition has its origins in the study of Schrödinger operators and is weaker than a lower bound assumptions. Our work provides an extension of the result of Cheeger and Colding. I will try to explain this condition, I will explain one of the crucial point that is the existence of a new familly of monotone quantities.