Jean-Paul has made important contributions to a variety of fields throughout his career. His review on "Nuclear compressibilities" (1980) and, more importantly, his textbook on "Quantum Theory of finite systems", coauthored with Georges Ripka (MIT Press, 1986), are classics. He was one of the pioneers of the application of hydrodynamics to ultrarelativistic heavy ion collisions (1983, with Baym, Friman, Soyeur); He was also among the first to address the early stage of ultrarelativistic heavy-ion collisions from first principles (1987, with Al Mueller).