Jacob Levy Moreno was an original and productive thinker of the 20th century. Beyond the development of psychodrama, sociometry, and group psychotherapy, he provided many impulses that have enriched today's psychology, sociology, and other sciences. On the occasion of his 125th birthday and 40th anniversary of his death, this book reflects on Moreno and his life's work: companions and contemporaries share their personal encounters with Moreno, historical analyses shed light on previously little-known aspects of Moreno's life, and ten contributions discuss the relevance of Moreno's work from the perspectives of various scientific disciplines and fields of application.