The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge. The experiment took place in the Ryerson Physical Laboratory at the University of Chicago. Millikan received the Nobel Prize in Physics in 1923.
Millikan's setup for the oil drop experiment
Oil drop experiment apparatus
Image: Scheme of Millikan’s oil drop apparatus
Robert Andrews Millikan was an American experimental physicist who won the Nobel Prize for Physics in 1923 for the measurement of the elementary electric charge and for his work on the photoelectric effect.
Millikan in 1923
Millikan's original oil-drop apparatus, circa 1909–1910
Robert A. Millikan around 1923
The former Millikan Library at Caltech in 2010 (renamed Caltech Hall in 2021)