This volume describes the wide-ranging scientific activities of Léon Van Hove, through commentaries by his colleagues and a selection of his most influential papers and documents. The reprinted papers are grouped by topic, starting from his early work in mathematics and theoretical and statistical physics, up to his very last contributions in elementary particle physics and multiparticle dynamics. Van Hove's career as teacher, director and science advisor in many European institutions is presented in sketches by friends and coworkers. A selection of his speeches and documented thoughts on science completes the volume.