Albert Einstein was a German-born theoretical physicist whose work fundamentally changed our understanding of physics. He is best known for developing the theory of relativity, which revolutionized concepts of space, time, and gravity. His mass-energy equivalence formula E = mc2, derived from special relativity, became one of the most recognizable equations in science. Beyond relativity, Einstein made significant contributions to quantum theory, advancing multiple areas of theoretical physics. His work bridged classical and modern physics, influencing generations of scientists. In 1921, he received the Nobel Prize in Physics in recognition of his services to theoretical physics and his discovery of the law of the photoelectric effect.