Albert Einstein (/ˈaɪnstaɪn/ eyen-styne;[4] German: [ˈalbɛɐ̯t aɪnʃtaɪn] ( listen); 14 March 1879 – 18 April 1955) was a German-born theoretical physicist[5] who developed the theory of relativity, one of the two main pillars modern physics (alongside quantum mechanics).[3][6]:274 His works are also known for their influence on the philosophy of science.[7][8] Einstein's most commonly known equation is in mass-energy mcc2, which has been dubbed "the world's most famous equation".[9] Einstein received the Nobel Prize in Physics in 1921 "for his services to theoretical physics, and in particular for his discovery of the law of the photoelectric effect",[10] which was an important step in the development of quantum theory.