  We discuss how the dynamics of the evolving hot fireball of quark--gluon
matter impacts phase transition between the deconfined and confined state of
matter. The rapid expansion of the fireball of deconfined matter created in
heavy ion collisions facilitates formation of an over-saturated strange quark
phase space. The related excess abundance of strangeness is compensating the
suppression of this semi-heavy quark yield by its quark mass. In addition, the
dynamical expansion of colored quanta pushes against the vacuum structure, with
a resulting supercooling of the transition temperature. We address the status
of the search for the phase boundary as function of reaction energy and
collision centrality and show evidence for a change in reaction mechanism at
sufficiently low energies. The phase diagram derived from the study of hadron
production conditions shows two boundaries, one corresponding to the expected
transition between confined and deconfined matter, with a downward temperature
shift, and the other a high quark density hadronization which appears to
involve heavy effective quarks, at relatively large temperatures.
