  We discuss medium effects on light cluster production in the QCD phase
diagram within a generalized Beth-Uhlenbeck (GBU) approach by relating Mott
transition lines to those for chemical freeze-out. We find that in heavy-ion
collisions at highest energies provided by the LHC light cluster abundances
should follow the statistical model because of low baryon densities. At low
energies in the nuclear fragmentation region, where the freeze-out interferes
with the liquid-gas phase transition, selfenergy and Pauli blocking effects are
important. At intermediate energies the HADES, FAIR and NICA experiments can
give new information. The GBU approach provides new insights to strange hadron
production in this energy domain for explaining the "horn" effects.
