In the last four chapters, we have examined the individual components that constitute AGNs. At this point, it is worth briefly summarizing these as we proceed to develop a more global picture of the AGN phenomenon. Although direct proof is lacking, the evidence points towards gravitational accretion of matter by supermassive black holes as being the primary energy source in AGNs. Gravitational potential energy is converted into radiation via viscous dissipation in an accretion disk surrounding the black hole. For a luminous Seyfert galaxy, the black-hole mass is inferred to be something like ∼ 107M⊙ (i.e., RS ≲ 1013 cm), and the UV/optical continuum-emitting region of the purported accretion disk is smaller than ∼ 1015 cm. The corresponding X-ray-emitting region appears to be smaller still, perhaps only several times RS. Surrounding this is the BLR, which has a typical size of 1016cm or so, but whose specific geometry and kinematics are poorly known. It appears that most of the IR continuum emission arises on spatial scales larger than the dust sublimation radius (≳ 1017 cm). This is also where we find the lower-density NLR, where the gas motions are dominated by gravity, but where we also see evidence for interaction with jets in the form of shock-heating and outflowing gas.