  Deep X-ray surveys are providing crucial information on the evolution of AGN
and galaxies. We review some of the latest results based on the X-ray spectral
analysis of the sources detected in the Chandra Deep Field South, namely: i)
constraints on obscured accretion; ii) constraints on the missing fraction of
the X-ray background; iii) the redshift distribution of Compton-thick sources
and TypeII QSO; iv) the detection of star formation activity in high-z galaxies
through stacking techniques; v) the detection of large scale structure in the
AGN distribution and its effect on nuclear activity. Such observational
findings are consistent with a scenario where nuclear activity and star
formation processes develop together in an anti-hierarchical fashion.
