Problems of investigating nuclear matter properties at extremely large densities and temperatures were already being raised until QCD was formulated as a theory describing the strong interactions (see, for example, [157, 158]). After the confinement and asymptotic freedom have been discovered it was realized very quickly that in nuclear matter at extreme conditions (strongly compressed and/or heated hadronic matter), a state with the deconfinement of quarks and gluons may exist. The term quark gluon plasma itself appears to have been introduced in Ref. [159], where it was shown that this state may come into being under collisions of heavy ions when the energy density of colliding ions reaches the value of the order of 1 GeV/fm3.