In atomic nuclei, because of their larger dimensions as compared with nucleons, statistical and thermodynamical concepts have been used already in the 1930s. Hans Bethe had suggested that propagation of heat in nuclear matter could be studied in central collisions and Sin-Itiro Tomonaga had calculated the corresponding heat conductivity. The interest in this phenomenon was resurrected in the 1970s by the work of Weiner and Weström who established the link between the hot spot model and the pre-equilibrium approach used in low-energy heavy-ion reactions. Experimentally the hot spot model in nuclear reactions was confirmed in a series of investigations some of which of rather sophisticated nature including polarization measurements of protons and gamma rays. Subsequently on the theoretical side the link between hot spots and limiting fragmentation and transparency in high-energy heavy ion reactions was analyzed and “drifting hot spots” for central collisions were studied. With the advent of heavy ion accelerators experimental studies of hot spots in nuclear matter became a subject of current interest and a series of special meetings was dedicated to the topic of local equilibrium in strong interactions. The phenomena of hot spots, heat conduction and preequilibrium play also an important part in high-energy heavy ion reactions and in the search for the phase transition to quark matter.