Electron charge

Balancing gravity against electric attraction, Millikan accurately measured the electric charge of an electron by observing oil droplets ionized by X-rays. The charge on a single electron turns out to be sixteen-quintillionths of a coulomb.
 Robert Andrews Millikan United States 1911 Electron charge

Balancing gravity against electric attraction, Millikan accurately measured the electric charge of an electron by observing oil droplets ionized by X-rays. The charge on a single electron turns out to be sixteen-quintillionths of a coulomb.