Dynamics and Origin of the Milky Way Bulge

The inner Milky Way is dominated by a box/peanut shaped bulge believed
to have formed through disk instability processes.  Recent photometric
and spectroscopic surveys have greatly increased our understanding of
its spatial, kinematic, and metallicity structure. Formation models
are broadly consistent with these data, although many aspects still
need to be worked out.  There appears to be little evidence for a
merger-built classical bulge: the Milky Way may have started out as a
pure disk galaxy.