  Probing the growth of structure from the epoch of hydrogen recombination to
the formation of the first stars and galaxies is one of the most important
uncharted areas of observational cosmology. Far-IR spectroscopy covering
$\lambda$ 100-500 microns from space, and narrow partial transmission
atmospheric bands available from the ground, opens up the possibility of
probing the molecular hydrogen and metal fine-structure lines from primordial
clouds from which the first stars and galaxies formed at 6 < z $<$ 15. Building
on Spitzer observations of unexpectedly powerful H2 emission from shocks, we
argue that next-generation far-IR space telescopes may open a new window into
the main cloud cooling processes and feedback effects which characterized this
vital, but unexplored epoch. Without this window, we are essential blind to the
dominant cloud cooling which inevitably led to star formation and cosmic
reionization.
