Albert Einstein (March 14, 1879 – April 18, 1955) was a German-born theoretical physicist best known for developing the theory of relativity. He also made significant contributions to quantum mechanics. His mass-energy equivalence formula, E = mc², which stems from special relativity, has been called “the world’s most famous equation.” In recognition of his contributions to theoretical physics, particularly his discovery of the law of the photoelectric effect, he was awarded the Nobel Prize in Physics in 1921.