Albert Einstein is renowned in physics for developing the theory of **relativity**, which revolutionized the understanding of time, space, and gravity. His most famous equation, E=mc², describes the equivalence of mass and energy. This groundbreaking work fundamentally changed the field of theoretical physics and provided new insights into the nature of the universe. Relativity comprises two parts: special relativity, focusing on the physics of objects moving at constant speeds, particularly at the speed of light, and general relativity, which expands these concepts to include acceleration and gravitation.