Abstract
In this thesis, I am studying the heterogeneous dynamics and aging phenomena in colloidal suspensions of hard spheres and quasi-hard spheres model. These phenomena are studied by means of dynamic light scattering techniques and by molecular dynamics simulations. The experimental measurement of the induced fluctuations of the dynamics gives a quantitative estimation of the size of the cooperative regions. Simulations confirm these results. <br />In the out of equilibrium study, we show that the concentrated colloidal suspensions can be equilibrated if the measurement time is sufficiently large, that is about ten times larger than the characteristic relaxation time.