  A wide range of observational and theoretical arguments suggest that the
universe experienced a period of heating and metal enrichment, most likely from
starbursting dwarf galaxies. Using a hydrodynamic simulation we have conducted
a uniquely detailed theoretical investigation of this epoch at the end of the
cosmological ``dark ages''. Outflows strip baryons from pre-viralized halos
with total masses $\lesssim10{}^{10}$ M${}_\odot$, reducing their number
density and the overall star formation rate, while pushing these quantities
toward their observed values. We show that the metallicity of
$\lesssim10{}^{10}$ M${}_\odot$ objects increases with size, but with a large
scatter, reproducing the metallicity-luminosity relation of dwarf galaxies.
Galaxies $\gtrsim10{}^{10}$ M${}_\odot$ form with a roughly constant initial
metallicity of 10% solar, explaining the observed lack of metal-poor disk stars
in these objects. Outflows enrich roughly 20% of the simulation volume,
yielding a mean metallicity of 0.3% solar, in agreement with observations of
CIV in QSO absorption-line systems.
