  We review the properties of the established Scaling Relations (SRs) of
galaxies and active galactic nuclei (AGN), focusing on their origin and
expected evolution back in time, providing a short history of the most
important progresses obtained up to now and discussing the possible future
studies. We also try to connect the observed SRs with the physical mechanisms
behind them, examining to what extent current models reproduce the
observational data. The emerging picture clarifies the complexity intrinsic to
the galaxy formation and evolution process as well as the basic uncertainties
still affecting our knowledge of the AGN phenomenon. At the same time, however,
it suggests that the detailed analysis of the SRs can profitably contribute to
our understanding of galaxies and AGN.
