Robert Andrews Millikan, an American physicist, discovered the charge carried by the electron, an elementary particle, in 1910. He made this discovery by conducting an experiment called the oil-drop experiment.
Millikan enjoyed considerable success in his career as a physicist. In 1916 he confirmed the validity of equations, developed by Albert Einstein, regarding the photoelectric effect. During the early 1920s, Robert Millikan studied cosmic rays and established that they came from locations external to the earth. He was awarded the Nobel Prize in physics in 1923. During his time on the executive council at the California Institute of Technology, he was instrumental in turning Caltech into a leading American research institute.