Joseph John Thomson was a British physicist born on December 18, 1856. He is best known for discovering the electron, a fundamental particle that is a key component of atoms. His work in the late 19th century laid the foundation for modern atomic theory and earned him the Nobel Prize in Physics in 1906. Thomson also developed the plum pudding model of the atom, which proposed that atoms are composed of a positively charged "soup" with negatively charged electrons embedded within it. This model was later replaced by the nuclear model proposed by Ernest Rutherford, but Thomson's contributions significantly advanced the field of particle physics.