Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, revolutionizing physics in the early 20th century. Some of his most influential works included developing the photoelectric effect, mass-energy equivalence with E=mc2, and introducing the concept of photons that helped establish quantum theory. He received the 1921 Nobel Prize in Physics for his services to theoretical physics, particularly his discovery of the law of the photoelectric effect. Einstein is considered one of the most influential physicists of the 20th century and revolutionized how we understand space, time, gravity and the universe.