We present Vlasov's equation and its association with Poisson's equation in the context of modelling self-gravitating systems such as Globular Clusters or Galaxies. We first review the classical hypotheses of the model. We continue with a presentation of the Hamilton-Morrison structure of Vlasov's equation to study the equilibrium and the stability of self-gravitating systems. Finally, we present some preliminary results concerning some properties of the time dependent solutions of the Vlasov-Poisson system.