They are subatomic particles that surround the nucleus of a cell and are negatively charged.
J.J Thomson based on his work with the discharge tube, identified the electrons.
He set up two plates with completely opposite charges close to the cathode rays.
When high voltage was applied cathode rays were directed away from the negatively charged plate and toward the positively charged plate.
This suggested that cathode rays were made up of negatively charged electrons, which are now known as electrons, as opposing charges attract one other and like charges repel each other.
Therefore, electrons were discovered by J.J Thomson