Albert Einstein (1879–1955) was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics). Although relativity is his most widely remembered achievement, he published more than 300 scientific papers (along with over 150 non-scientific works), and the Nobel Prize in Physics he received in 1921 was "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"—a pivotal step in the evolution of quantum theory.Photograph: Ferdinand Schmutzer; restoration: Adam Cuerden