With no known substructure, electrons are subatomic elementary particles. The negative charge of electrons balances out the positive charge of protons in the atomic nucleus. At almost 1000 times smaller than a proton, electrons are extremely low in mass.
This video explores the discovery and contributions to the understanding of subatomic particles by scientists such as Niels Bohr. Bohr developed the Bohr model of the atom in which he theorised electrons revolved around the atomic nucleus in stable orbits. The Bohr model has since been usurped by more comprehensive models but its core principles remain valid.