Designed and performed by American physicist R.A. Millikan, the Oil Drop Experiment is a very important experiment in the history of Modern Physics. It proved beyond doubt the discreteness of the charge -- only integral multiples of the charge exist, and measured the unitary charge accurately. It also provided a possibility to measure other basic physics quantities.
Millikan Oil Drop Experiment had always been viewed as a classic and inspiring experiment because of its design, simplicity, clarity and accuracy. It was repeated by hundreds of thousands of university (even high school) students in their physics labs all over the world and it had been improved students skills and abilities in carrying out experiments.