Geneticist and Nobel prize laureate. Muller was born and schooled in New York City, receiving an A.B., M.A. and in 1915 his Ph.D. from Columbia University. His first faculty appointment was at Rice University in Houston, Texas. He then accepted a two-year appointment as instructor at Columbia hoping it would lead to a permanent position. In 1920, however, Muller accepted an offer from the University of Texas. In Austin his experiments on fruit flies (Drosophila) first showed that exposure to radiation caused mutation in living organisms. This work would earn Muller the 1946 Nobel Prize in Physiology or Medicine.

Muller applied for and won a Guggenheim fellowship in 1932 and left the U.S. in September to spend a year at the only Drosophila laboratory in Europe which was doing parallel work, Berlin's Kaiser Wilhelm Institute for Brain Research. As the Nazi take over of the German government, the persecution of Jews, and the burning of forbidden books increased through 1933, Muller accepted a position at the Institute of Genetics in Leningrad. He had been elected a corresponding member of the Soviet Academy of Sciences, under whose auspices and budget basic research was carried out in the USSR, and in Leningrad for the first time he had an appointment as a full-time research scientist without teaching responsibilities. In December, 1934, he and his research group moved to Moscow. By 1936 Stalin was beginning his reign of terror with hundreds of arrests and executions, including prominent scientists who were falsely accused of Trotskyism. Stalin began influencing the outcome of scientific research and bitter disagreements with Trofim D. Lysenko, whose theories on genetics reflected party line politics, pushed Muller to enlist in the Spanish Republican cause as the best way of getting out of the Soviet Union. Although he worked for just eight weeks in Madrid during the spring of 1937, his service provided the immunity he needed for a permanent departure from the USSR in good standing and with the least damage to the reputations of his Russian colleagues.

After leaving the Soviet Union in September 1937, Muller spent some weeks in Paris at Boris Ephrussi's laboratory before accepting an offer from F.A.E. Crew at the Institute of Animal Genetics in Edinburgh. Originally a temporary appointment, Muller was soon awarded a three-year Macauley Research Fellowship as well as some supplemental Rockefeller Foundation support to run his laboratory. It was during this period that he met a young German refugee named Dorothea Kantorowicz who had been appointed as a technician in the Institute's pregnancy laboratory. They were married in May 1939. The outbreak of war later that year greatly affected the working habits of the institute, and Crew initiated a determined effort to get Muller and his research placed in an American university. Despite failing to obtain any position offers the Mullers left for New York , via Lisbon, in September 1940. A month later Harold Plough offered Muller a temporary position at Amherst College in Massachusetts, an undergraduate liberal-arts college. Following the attack on Pearl Harbor Plough left Amherst for full-time service as bacteriologist with the U.S. Army and Muller was then given an indefinite appointment as a professor of biology; however that appointment was ultimately determined to end in June 1945. Following a visit to Bloomington, Indiana, and interviews with zoology department faculty and President Herman B Wells, Muller was offered an appointment as research professor, meaning that he would do as much graduate teaching as he desired but would not be expected to do any undergraduate teaching. Muller remained at Indiana University until his retirement in 1964.

A year after his arrival at Indiana Muller received the Nobel Prize. He received many more awards and tributes over the years, including the Bossom Award, the Kimber Genetics Award, and several honorary doctorates. His death in 1968 came just two months before he would have received Indiana's honorary degree voted him by the Faculty Council and approved by the Trustees the year before. Muller was active in numerous scientific organizations and was in contact both personally and professionally with the leading geneticists and biologists of the day. Some correspondents represented in the collection include: Edgar Altenburg, Charlotte Auerbach, Gert Bonnier, Herbert Brewer, Cyril Dean Darlington, Max Delbrück, Milislav Demerec, Theodosius Dobzhansky, Carl Gottfried Hartman, Lancelot Hogben, Alexander Hollaender, Sir Julian Huxley, Joshua Lederberg, Salvador Edward Luria, Otto Lous Mohr, Gregory Pincus, Guido Pontecorvo, Carl Sagan, Tracy Sonneborn, Alfred Henry Sturtevant, Leo Szilard, Nikolai Vladimirovich Timoféev-Resovskii, and Nikolai Ivanovich Vavilov.