We present in this proceeding recent large scale simulations of dense colloids. On one hand we simulate model clay consisting of nanometric aluminum oxide spheres in water using realistic DLVO potentials and a combination of MD and SRD. We find pronounced cluster formation and retrieve the shear softening of the viscosity in quantitative agreement with experiments. On the other hand we study the velocity distribution functions (PDF) of sheared hard-sphere colloids using a combination of MD with lattice Boltzmann and find strong deviations from a Maxwell-Boltzmann distribution. We find a Gaussian core and an exponential tail over more than six orders of magnitude of probability. The simulation data follow very well a simple theory. We show that the PDFs scale with shear rate as well as particle volume concentration, and kinematic viscosity.