In the first years after the discovery of radioactivity it became clear that nuclear physics was, by excellence, the science of small quantum systems. Between the fifties and the eighties nuclear physics and elementary particles physics lived their own lives, without much interaction. During this period the basic concepts were defined. Recently, contrary to the specialization law often observed in science, the overlap between nuclear and elementary particle physics has become somewhat blurred. This Les Houches Summer School was set up with the aim of fighting off the excessive specialization evident in many international meetings, and return to the roots. The twofold challenge of setting up a fruitful exchange between experimentalists and theorists in the first place, and between nuclear and hadronic matter physicists in the second place was successfully met. The volume presents high quality, up-to-date reviews starting with an account of the birth and first developments of nuclear physics. Further chapters discuss the description of the nuclear structure, the physics of nuclei at very high spin, the existence of super-heavy nuclei as a consequence of shell structure, liquid-gas transition, including both a description and a review of the experimental situation. Other topics dealt with include the interactions between moderately relativistic heavy ions, the concept of a nucleon dressed by a cloud of pions, the presence of pions in the nucleus, the subnucleonic phenomena in nuclei and quark-gluons deconfinement transition, both theoretical and experimental aspects. Nuclear physics continues to influence many other fields, such as astrophysics, and is also inspired by these same fields. This cross-fertilisation is illustrated by the treatment of neutron stars in one of the final chapters. The last chapter provides an overview of a recent development in which particle and nuclear physicists have cooperated to revitalize an alternative method for nuclear energy production associating high energy production accelerators and sub-critical neutron multiplying assemblies.