  Recent results connected to nuclear collision dynamics, from low up to
relativistic energies, are reviewed. Heavy ion reactions offer the unique
opportunity to probe the complex nuclear many-body dynamics and to explore, in
laboratory experiments, transient states of nuclear matter under several
conditions of density, temperature and charge asymmetry. From the theoretical
point of view, transport models are an essential tool to undertake these
investigations and make a connection between the nuclear effective interaction
and sensitive observables of experimental interest. In this article, we mainly
focus on the description of results of transport models for a selection of
reaction mechanisms, also considering comparisons of predictions of different
approaches. This analysis can help understanding the impact of the interplay
between mean-field and correlation effects, as well as of in-medium effects, on
reaction observables, which is an essential point also for extracting
information on the nuclear Equation of State. A special emphasis will be given
to the review of recent studies aimed at constraining the density behavior of
the nuclear symmetry energy. For reactions at medium (Fermi) energies, we will
describe light particle and fragment emission mechanisms, together with isospin
transport effects. Collective effects characterizing nuclear collision
dynamics, such as transverse and elliptic flows, will be discussed for
relativistic heavy ion reactions, together with meson production and isotopic
ratios.
