  In the standard Cold Dark Matter (CDM) theory of structure formation,
virialized minihalos (with T_vir = 10,000 K or less) form in abundance at high
redshift (z > 6), during the cosmic "dark ages." The hydrogen in these
minihalos, the first nonlinear baryonic structures to form in the universe, is
mostly neutral and sufficiently hot and dense to emit strongly at the 21-cm
line. We calculate the emission from individual minihalos and the radiation
background contributed by their combined effect. Minihalos create a "21-cm
forest" of emission lines. We predict that the angular fluctuations in this
21-cm background should be detectable with the planned LOFAR and SKA radio
arrays, thus providing a direct probe of structure formation during the "dark
ages." Such a detection will serve to confirm the basic CDM paradigm while
constraining the background cosmology parameters, the shape of the
power-spectrum of primordial density fluctuations, the onset and duration of
the reionization epoch, and the conditions which led to the first stars and
quasars. We present results here for the currently-favored, flat LCDM model,
for different tilts of the primordial power spectrum. These minihalos will also
cause a "21-cm forest" of absorption lines, as well, in the spectrum of radio
continuum sources at high redshift, if the latter came into existence before
the end of reionization.
