In this talk, we focus on the mean field limit and propagation of chaos for large systems of particles with singular interacting forces. We use the relative entropy method to quantify the propagation of chaos for large stochastic or deterministic systems of interacting particles. This approach requires to prove large deviations estimates for non-continuous potentials modified by the limiting law. But it leads to explicit convergence rates for all marginals. Recent successes include the Vlasov systems with bounded interaction forces, the 2D Navier-Stokes system, the Patlak-Keller-Segel system and others. This talk involves years’ collaborations with P.-E. Jabin and also recently with D. Bresch.