  The discoveries made over the past 20 years by Chandra and XMM-Newton surveys
in conjunction with multiwavelength imaging and spectroscopic data available in
the same fields have significantly changed the view of the supermassive black
hole (SMBH) and galaxy connection. These discoveries have opened up several
exciting questions that are beyond the capabilities of current X-ray telescopes
and will need to be addressed by observatories in the next two decades. As new
observatories peer into the early Universe, we will begin to understand the
physics and demographics of SMBH infancy (at $z>6$) and investigate the
influence of their accretion on the formation of the first galaxies ($\S$ 2.1).
We will also be able to understand the accretion and evolution over the cosmic
history (at $z\sim$1-6) of the full population of black holes in galaxies,
including low accretion rate, heavily obscured AGNs at luminosities beyond the
reach of current X-ray surveys ($\S$2.2 and $\S$2.3), enabling us to resolve
the connection between SMBH growth and their environment.
