Next, he verified experimentally Einstein's all-important photoelectric equation, and made the first direct photoelectric determination of Planck's constant h (1912-1915). His earliest major success was the accurate determination of the charge carried by an electron, using his 'falling-drop method' he also proved that this quantity was a constant for all electrons (1910), thus demonstrating the atomic structure of electricity. Millikan made numerous discoveries in the fields of electricity, optics, and molecular physics. During his early years at Chicago, he spent much time preparing textbooks and simplifying the teaching of physics. Millikan was an eminent teacher, and passing through the customary grades he became professor at that university in 1910, a post which he retained until 1921.

Michelson, to become assistant at the newly established Ryerson Laboratory at the University of Chicago. Millikan spent a postgraduate year (from 1895-1896) in Germany, at the Universities of Berlin and Gottingen.

In 1893, after obtaining his mastership in physics, he was appointed Fellow in Physics at Columbia University. It was during this period that he developed his interest in the subject in which he was later to excel. During his undergraduate course at Oberlin College, his favorite subjects were Greek and mathematics but after his graduation in 1891 he took, for two years, a teaching post in elementary physics. Robert Andrews Millikan was born in Morrison, Illinois, in 1868.

Robert millikan atomic theory