  We simulate a plausible cosmological model in considerable physical and
numerical detail through the successive phases of reheating (at 10<z<20),
formation of Pop III stars at z=15 (due to molecular hydrogen cooling), with
subsequent reionization at z=7. We assume an efficiency of high mass star
formation appropriate to leave the universe, after it becomes transparent, with
an ionizing background J_21=0.4 (at z=4), near (and perhaps slightly below) the
observed value. Since the same stars produce the ionizing radiation and the
first generation of heavy elements, a mean metallicity of Z/Z_\sun=1/200 is
produced in this early phase, but there is a large variation about this mean,
with the high density regions having Z/Z_\sun=1/30 and low density regions
essentially no metals.
  Reionization, when it occurs, is very rapid, which will leave a signature
which may be detectable by very large area meter-wavelength radio instruments.
Also, the background UV radiation field will show a sharp drop from 1Ryd to
4Ryd due to absorption edges.
  The simulated volume is too small to form L_* galaxies, but the smaller
objects which are found in the simulation obey the Faber-Jackson relation.
  In order to explore theoretically this domain of "the end of the dark ages"
quantitatively, numerical simulations must have a mass resolution of the order
of 10^{4.5} M_\sun} in baryons, high spatial resolution (1 kpc) to resolve
strong clumping, and allow for detailed and accurate treatment of both the
radiation field and atomic/molecular physics.
