Joseph John Thomson was a pioneering British physicist best known for discovering the electron in 1897, a breakthrough that revolutionised atomic theory.

Born on December 18, 1856, in Cheetham Hill, Manchester, Thomson studied at Owens College before earning a scholarship to Trinity College, Cambridge. He became Cavendish Professor of Experimental Physics in 1884, succeeding Lord Rayleigh, and held the position until 1919. His most famous work involved experiments with cathode rays, which led him to identify particles smaller than atoms—later named electrons. This discovery challenged the prevailing notion that atoms were indivisible and laid the foundation for modern particle physics.

Thomson also proposed the plum pudding model of the atom, envisioning electrons embedded in a positively charged sphere. Though later replaced by more accurate models, it was a crucial step in atomic theory. He invented the mass spectrograph, enabling the identification of isotopes, and mentored future Nobel laureates, including his son, George Paget Thomson.

In 1906, Thomson received the Nobel Prize in Physics for his work on the conduction of electricity in gases. He died on August 30, 1940, in Cambridge, leaving behind a legacy that transformed our understanding of matter and inspired generations of physicists.