Large scale structure of the Universe. Formation and dynamics of the cosmic web of clusters and groups of galaxies. simple collapse models for the dark matter. Physics of intergalactic and intracluster gas. Heating and cooling mechanisms. Chemical enrichment of intergalactic and intracluster gas. Observations of clusters of galaxies in X-ray and microwave bands, Ly_alpha and X-ray-forest. Estimate of the mass of clusters of galaxies: dynamical methods, observations in X-ray and microwave bands, gravitational lenses. Cosmology with clusters of galaxies: mass function, scaling laws.