This project aims at studying, from the mathematical point of view, certain singular asymptotic regimes for Vlasov equations, that is to say for kinetic transport equations without collision. The asymptotic regimes we would like to consider are of two different nature: firstly large time behavior of solutions, in which case one wants to describe the final dynamics and the speed of convergence, secondly certain scaling limits where some physical quantites are seen as small parameters, in which case the aime to exhibit an effective limit equation. The underlying idea is to consider in a joint way these two types of problems.. The point is to exhibit formal links and to rely on them to obtain original new methods. We wish to tackle singular problems where classical methods cannot be used; singularities can come either from the lack of regularity of some limit objects, or from degeneracy coming from the structure of the equations themselves / We wish to focus in particular on the following problems: - Landau damping and quasineutral limit for the Vlasov-Poisson system; - Monokinetic behavior and high friction limits for the Vlasov-Navier-Stokes system.