A native of Illinois, Robert Millikan was born March 22, 1868. He studied physics at Oberlin College and later at Columbia University where he obtained his Ph.D. in 1895. His doctoral research involved the polarization of light emitted by incandescent surfaces. He spent a year in Germany at the Universities of Berlin and Göttingen and returned to the U.S. to join the physics faculty at the University of Chicago.

In 1907, he began taking measurements of the electronic charge of an electron. Earlier researchers had studied the behavior of clouds of charged particles, but he investigated single drops of water and oil in electrical and gravitational fields. From those, he derived the first accurate value of e. 

Millikan’s major optics contribution came in 1916 when he turned his attention to the photoelectric equation of Einstein (E =hv). By varying both energies and frequencies, he obtained an accurate value for the Planck constant h. For his determinations of atomic structure of electrons and the photoelectric effect he earned the Nobel Prize in physics in 1923. He also did much subsequent work on cosmic rays.

During World War I, Millikan was vice-chairman of the National Research Council, and played a major part in developing anti-submarine and meteorological devices. From 1921 until 1945, he was chairman of the California Institute of Technology.

Quite active in promoting scientific activities, Millikan was president of the American Physical Society, vice-president of the American Association for the Advancement of Science, and was the American member of the Committee on Intellectual Cooperation of the League of Nations, and the American representative at the International Congress of Physics, known as the Solvay Congress, at Brussels in 1921.

He held honorary doctor's degrees of 25 universities, and was a member or honorary member of many learned institutions in his country and abroad. He was the recipient of the Comstock Prize of the National Academy of Sciences, the Edison Medal of the American Institute of Electrical Engineers, and the Hughes Medal of the Royal Society of Great Britain. He was also made Commander of the Legion of Honor, and received the Chinese Order of Jade.

Millikan died in December 19, 1953.