  Many new particles, mostly hadrons, are produced in high energy collisions
between atomic nuclei. The most popular models describing the hadron production
process are based on the creation, evolution and decay of resonances, strings
or quark-gluon plasma. The validity of these models is under vivid discussion,
and it seems that a common framework for this discussion is missing. Here we
introduce the diagram of high energy nuclear collisions, where domains of the
dominance of different hadron-production processes in the space of
laboratory-controlled parameters, the collision energy and nuclear-mass number
of colliding nuclei, are indicated. We argue, the recent experimental results
locate boundaries between the domains, allowing for the first time to sketch an
example diagram. Finally, we discuss the immediate implications for
experimental measurements and model development following the sketch.
