Revisiting the Unified Model of Active Galactic Nuclei
  This review describes recent developments related to the unified model of
active galactic nuclei (AGN). It focuses on new ideas about the origin and
properties of the central obscurer (torus), and the connection with its
surrounding. The review does not address radio unification. AGN tori must be
clumpy but the uncertainties about their properties are still large. Todays
most promising models involve disk winds of various types and hydrodynamical
simulations that link the large scale galactic disk to the inner accretion
flow. IR studies greatly improved the understanding of the spectral energy
distribution of AGNs but they are hindered by various selection effects. X-ray
samples are more complete. A basic relationship which is still unexplained is
the dependence of the torus covering factor on luminosity. There is also much
confusion regarding "real type-II AGNs" that do not fit into a simple
unification scheme. The most impressive recent results are due to IR
interferometry, which is not in accord with most torus models, and the accurate
mapping of central ionization cones. AGN unification may not apply to merging
systems and is possibly restricted to secularly evolving galaxies.
