Max Delbrück was born on September 4th, 1906, in Berlin, Germany, the youngest of seven children. His father, Hans Delbrück, Professor of History at the University of Berlin, was for many years editor and political columnist of the Preussische Jahrbücher. His mother was a granddaughter of the chemist, Justus von Liebig.

Max Delbrück grew up in a suburb of Berlin (Grunewald) populated by moderately affluent members of the academic, professional, and merchant community, many of them with large families. The period of affluence and lively hospitality before 1914 was followed by the war years with hunger, cold, and death, and the postwar period of revolution, inflation, and impoverishment.

His interest in science dates back to boyhood and was directed first towards astronomy, which he seized upon as a means of finding an identity in an environment of strong personalities. All senior to him, many with high accomplishments, none was in the sciences. The one exception, the oldest boy in the Bonhoeffer family, Karl Friedrich (his father Karl Bonhoeffer was Professor of Psychiatry), eight years older than Max Delbrück, was a physical chemist of high distinction, and became the mentor and lifelong friend of Delbrück. The shift to theoretical physics during the latter part of his graduate studies in Göttingen was an easy one from astrophysics and a natural one in the late twenties, just after the breakthrough of quantum mechanics, for which Göttingen was one of the centers.

Among his friendships during the later student years, the most intense and influential one was with Werner Brock, now emeritus Professor of Philosophy, Freiburg.

There followed three postdoctoral years (1929-1932) abroad, in England, Switzerland, and Denmark. The stay in England, with its immersion into a new language and a new culture, had a vast effect on widening his outlook on life. In Switzerland and Denmark the associations with Wolfgang Pauli and Niels Bohr shaped his attitude toward the pursuit of truth in science.

Delbrück's interest in biology was first aroused by Bohr, in connection with his speculations that the complementarity argument of quantum mechanics might have wide applications to other fields of scientific endeavor and especially in regard to the relations between physics and biology. A move to Berlin in 1932, as assistant to Lise Meither, was largely motivated by the hope that the proximity of the various Kaiser Wilhelm Institutes to each other would facilitate the beginning of an acquaintance with the problems of biology. Paradoxically, this good intention was helped by the rise of Nazism which made official seminars less interesting. A small group of physicists and biologists began to meet privately beginning about 1934. To this group belonged N. W. Timofeeff-Ressovsky (genetics). Out of these meetings grew a paper by Timofeeff, Zimmer, and Delbrück on mutagenesis. A popularization of this paper of 1935 in Schroedinger's little book «What is Life?» (1945) had a curiously strong influence on the development of molecular biology in the late 1940's.

The move to the United States in 1937 was made possible by a second fellowship of the Rockefeller Foundation, permitting Delbrück to pursue with greater freedom and effectiveness his interests in biology. He chose Caltech because of its strength in Drosophila genetics, and to some extent because of its distance from the impending perils at home. Although his job in Germany seemed reasonably secure, it was clear that political reasons would bar him from advancement.

At Caltech he soon teamed up with E. L. Ellis doing phage research. The fellowship of the Rockefeller Foundation ran out in September 1939. World War II had started and Delbrück elected to stay in the United States. He accepted an instructorship in the Physics Department at Vanderbilt University in Nashville, Tennessee. The years at Vanderbilt were the war years. Both Luria (at Bloomington, Indiana) and Delbrück (at Vanderbilt) were technically enemy aliens, a status affording them the privacy to concentrate on science.

In 1941 Delbrück married Mary Bruce. She has given his life the harmony needed for its fulfillment. They have four children - a first set, Jonathan and Nicola, born in 1947 and 1949, and, since these turned out so happily, a second set, Tobias and Ludina, born in 1960 and 1962.

Since the early 1950's Delbrück's research interests have shifted from molecular genetics to sensory physiology and especially to the idea of introducing here, too, a microorganism of suitable simplicity. He turned to the sporangiophores of Phycomyces as a model system for the study of stimulus transductions. The goal of clarifying the molecular nature of the primary transducer processes of sense organs in general and of Phycomyces in particular has held his attention since then, with one interruption.

This interruption was the setting up of an institute of molecular genetics at the University of Cologne. Delbrück's goal was to demonstrate the feasibility of modern interdisciplinary research and of the «department system» (with several professors in one institute) within a German university setup, and to boost molecular genetics in Germany.

The Institut für Genetik der Universität Köln was formally dedicated on June 22nd, 1962, with Niels Bohr as the principal speaker. His lecture entitled «Light and Life - Revisited» commented on his original one of 1933, which had been the starting point of Delbrück's interest in biology. It was to be Bohr's last formal lecture. He died before completing the preparation of the manuscript of this lecture for publication.

Since 1964 the experimental work on Phycomyces is once more being pursued with full force, together with theoretical studies on related systems.

From Nobel Lectures, Physiology or Medicine 1963-1970.

Dr Delbrück died in 1981.