* J.J. Thomson: He is credited with discovering the electron in 1897. His experiments using cathode ray tubes demonstrated that electrons were negatively charged particles with a specific charge-to-mass ratio (e/m).
* Robert Millikan: In 1909, Millikan performed his famous oil drop experiment. This experiment measured the charge of a single electron, which allowed scientists to calculate the mass of the electron using the previously determined e/m value from Thomson's work.
Therefore, the combined work of Thomson and Millikan was crucial for determining the mass of an electron.
