  Over the last few years, both ALMA and Spitzer/IRAC observations have
revealed a population of likely massive galaxies at $z>3$ that was too faint to
be detected in HST rest-frame ultraviolet imaging. However, due to the very
limited photometry for individual galaxies, the true nature of these so-called
HST-dark galaxies has remained elusive. Here, we present the first sample of
such galaxies observed with very deep, high-resolution NIRCam imaging from the
Early Release Science Program CEERS. 30 HST-dark sources are selected based on
their red colours across 1.6 $\mu$m to 4.4 $\mu$m. Their physical properties
are derived from 12-band multi-wavelength photometry, including ancillary HST
imaging. We find that these galaxies are generally heavily dust-obscured
($A_{V}\sim2$ mag), massive ($\log (M/M_{\odot}) \sim10$), star-forming sources
at $z\sim2-8$ with an observed surface density of $\sim0.8$ arcmin$^{-2}$. This
suggests that an important fraction of massive galaxies may have been missing
from our cosmic census at $z>3$ all the way into the Reionization epoch. The
HST-dark sources lie on the main sequence of galaxies and add an obscured star
formation rate density (SFRD) of $\mathrm{3.2^{+1.8}_{-1.3} \times 10^{-3}
M_{\odot}/yr/Mpc^{3}}$ at $z\sim7$ showing likely presence of dust in the Epoch
of Reionization. Our analysis shows the unique power of JWST to reveal this
previously missing galaxy population and to provide a more complete census of
galaxies at $z=2-8$ based on rest-frame optical imaging.
