Albert Einstein is best known for the famous equation E=mc², which is a fundamental principle of his theory of relativity. This equation illustrates the relationship between mass (m) and energy (E), with "c" representing the speed of light in a vacuum. Essentially, it implies that mass can be converted into energy and vice versa, fundamentally changing the understanding of physics and our perception of the universe. Einstein introduced this equation in his 1905 paper on special relativity, significantly influencing modern physics and our comprehension of atomic energy, leading to advances in various scientific fields, including nuclear energy.