  At early times the Universe was filled up with an extremely dense and hot
gas. Due to the expansion it cooled below the binding energies of atoms which
led to the formation of the first nuclei. In the physical environment of the
post-recombination period of hydrogen, molecules such as $H_2$, $HD$ and $LiH$
can be formed. The proto-object formation, resulting from the growth of linear
density fluctuations in the early Universe, can have an important impact on the
chemical state of the Universe. Hence it can be enriched with metals, and thus
lead to the formation of the first pre-biotic molecules. In this contribution,
I will present some scheme for the formation of primordial molecules and
discuss the consequence of the formation of first stars on the existence of
possible primordial pre-biotic.
