The lectures presented deal with theories on the very early universe, capable of providing the initial conditions of the Friedmann model and of generating inhomogeneities in the inflationary period; modelling of the epoch of primordial nucleosynthesis. The properties of the cosmic microwave background are examined both its spectrum and the anisotropy at different angular scales. The book includes a state-of-the-art review of the large scale structure of statistical measurements of the distribution of galaxies, large-scale flows, the origin and distribution of voids and superclusters.