Albert Einstein's work fundamentally transformed modern physics, particularly through his theories of relativity. His 1905 paper on special relativity introduced the groundbreaking equation E=mc², establishing the equivalence of mass and energy. This challenged conventional views of space and time, proposing that they are interwoven in a four-dimensional continuum. Einstein's later work on general relativity reshaped the understanding of gravity, presenting it as a curvature of spacetime. His insights paved the way for advancements in fields like quantum mechanics and cosmology, influencing both theoretical frameworks and practical applications in technology.