  We investigate the 21 cm emission from the epoch between reionization z_r and
Gunn-Peterson transparency z_{gp}. According to the lognormal model of the
thermal history around reionization, hydrogen clouds in z_r > z > z_{gp} are
hot and a predominant part of baryonic gas is ionized, but still opaque to
Ly-alpha photons. Therefore, 21 cm emission is a distinctive characteristic of
this epoch. We show that the 21 cm emission comes from both uncollapsed and
collapsing hydrogen clouds. The spatial distribution of the brightness
temperature excess $\delta T_b$ is highly non-Gaussian. It consists of spikes
with high $\delta T_b$ and a low $\delta T_b$ area between the spikes. The
field has the following statistical features: (1) the one-point distributions
of $\delta T_b$ are described approximately by power-law tailed probability
distribution functions; (2) the nth-order moment of $\delta T_b$ is increasing
much faster with n than that of a Gaussian field, but slower than that of a
lognormal field; (3) the scale-scale correlation of the $\delta T_b$ field is
significant for all scales larger than the Jeans length of the gas. These
features would be useful for distinguishing the 21 cm emission of the early
clustering from the noise of foreground contamination.
