Who determined the charge-to-mass ratio $(e/m_e)$ of an electron and how? Explain.

(N/A) $J.J. \text{ Thomson}$ determined the value of $e/m_e$ by applying perpendicular electric and magnetic fields to the path of electrons in a cathode ray tube experiment.
$R.A. \text{ Millikan}$ determined the charge of an electron using the oil drop experiment.