The school is primarily addressed to Ph.D. students in Theoretical Nuclear and Hadron Physics. Participation of experimentalists and post-docs is also encouraged. The 2020 edition will be devoted to the strong interaction at finite temperature and density and it will provide a pedagogical introduction to the basic concepts and tools needed for carrying cutting edge research in Hot QCD matter, high energy QCD, Quark-Gluon Plasma probes and properties, ultra-relativistic nuclear collisions (pA, AA), Relativistic hydrodynamics, QCD phase diagram at finite temperature and chemical potential with applications to Neutron Stars physics and multi-messenger astrophysics.