Supermassive Black-Hole Growth Over Cosmic Time: Active Galaxy
  Demography, Physics, and Ecology from Chandra Surveys
  Extragalactic X-ray surveys over the past decade have dramatically improved
understanding of the majority populations of active galactic nuclei (AGNs) over
most of the history of the Universe. Here we briefly highlight some of the
exciting discoveries about AGN demography, physics, and ecology with a focus on
results from Chandra. We also discuss some key unresolved questions and future
prospects.
