Heavy-ion reactions at the GSI Darmstadt

In nucleus-nucleus collisions at bombarding energies on the order of 1 AGeV nuclear matter can be compressed to similar densities as encountered in stellar processes, i.e, to 2-3 times normal density. Experimental data providing information on the space-time evolution of these collisions are presented: the properties of hadrons in the hot and compressed nuclear medium in the high-density phase, collective flow phenomena during the expansion phase, and the hadrochemical composition of the collision system in the final stage of the reaction at freeze-out are discussed. Future directions in the heavy-ion reaction program are indicated.