The famous physicist who said, "E=mc²" is Albert Einstein. This equation, derived from his theory of relativity, expresses the equivalence of mass and energy, suggesting that a small amount of mass can be converted into a large amount of energy. It revolutionized the fields of physics and cosmology, altering our understanding of space, time, and gravity. Einstein's work laid the groundwork for many scientific advancements, including nuclear energy. Born in Germany in 1879, he made significant contributions to theoretical physics, and his theories remain foundational to modern physics, influencing countless aspects of science and technology today.