The talk is an introduction into diquark condensation phenomena which
occur in QCD at high energy density. They are driven by instantons and
instanton-antiinstanton pairs (or ''molecules''), which generate attr
action in some qq channels. A number of phases is possible, with or wi
thout restoration of chiral symmetry: the work is not finished and we
do not yet know which take place in real QCD. We also emphasize that s
pecific diquark correlations play a significant role in baryon structu
re, in particular making that of a nucleon very different of a Delta (
or other member of a decuplet). This ''small N-c'' scenario based on c
omparison to QCD with two colors is contrasted with the ''large N-c''
one.