  About 12 billion years ago, the Universe was first experiencing light again
after the dark ages, and galaxies filled the environment with stars, metals and
dust. How efficient was this process? How fast did these primordial galaxies
form stars and dust? We can answer these questions by tracing the Star
Formation Rate Density (SFRD) back to its widely unknown high redshift tail,
traditionally observed in the Near-InfraRed (NIR), Optical and UV bands. Thus,
the objects with a high amount of dust were missing. We aim to fill this
knowledge gap by studying Radio Selected NIR-dark (\textit{RS-NIRdark})
sources, i.e. sources not having a counterpart at UV-to-NIR wavelengths. We
widen the sample by Talia et al. (2021) from 197 to 272 objects in the COSMic
evolution Survey (COSMOS) field, including also photometrically contaminated
sources, previously excluded. Another important step forward consists in the
visual inspection of each source in the bands from u* to MIPS-24$\mu$m.
According to their "environment" in the different bands, we are able to
highlight different cases of study and calibrate an appropriate photometric
procedure for the objects affected by confusion issues. We estimate that the
contribution of RS-NIRdark to the Cosmic SFRD at 3$<$z$<$5 is $\sim$10--25$\%$
of that based on UV-selected galaxies.
