this volume collects the invited lectures and contributed talks of the nato advanced studies institute (asi) held in kemer/turkey, from 22nd september to 2 october 2003. the meeting brought together experts from several fields in nuclear physics in which rapid progress has been made in recent years. ultrarelativistic heavy ion collisions have been investigated at cern and at the relativistic heavy ion collider (rhic). several talks review the present status of experiments and develop the theory of nuclear reactions at ultrarelativistic collisions energies. the properties of hot and dense hadronic matter are studied and the predictions of quantum chromodynamics (qcd) for quark deconfinement and the phase transition to the quark gluon plasma are described. the dynamical description of phase transitions in small systems and the methods of nonequilibrium many body theory are covered by several speakers. furthermore the available information on the nuclear equation of state, the properties of cold dense quark matter, and colour superconductivity are presented in this volume. the close connection of these questions with astrophysics is drawn in several contributions related to the structure of stars, the dark matter problem, and the early universe. a second focal point of the asi, besides highly energetic heavy ion collisions, is the physics of exotic nuclei far off stability and superheavy elements. several leading experts in this field discuss the structure, the decay modes and lifetimes of superheavy nuclei both from the theoretical and the experimental points of view. additional topics are the description of fusion and fission processes, the properties of halo nuclei and nuclei beyond the line of particle stability.