  In the early Universe, strongly interacting matter was a quark-gluon plasma.
Both lattice computations and heavy ion collision experiments however tell us
that, in the absence of chemical potentials, no plasma survives at $T <\sim
150$ MeV. The cosmological Quark-Hadron transition, however, seems to have been
a crossover; cosmological consequences envisaged when it was believed to be a
phase transition no longer hold. In this paper we discuss whether even a
crossover transition can leave an imprint that cosmological observations can
seek or, viceversa, there are questions cosmology should address to QCD
specialists. In particular, we argue that it is still unclear how baryons (not
hadrons) could form at the cosmological transition. A critical role should be
played by diquark states, whose abundance in the early plasma needs to be
accurately evaluated. We estimate that, if the number of quarks belonging to a
diquark state, at the beginning of the cosmological transition, is $<\sim
1:10^6$, its dynamics could be modified by the process of B-transfer from
plasma to hadrons. In turn, by assuming B-transfer to cause just mild
perturbations and, in particular, no entropy input, we study the deviations
from the tracking regime, in the frame of SCDEW models. We find that, in some
cases, residual deviations could propagate down to primeval nuclesynthesis.
