Albert Einstein was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics. He is best known for his mass-energy equivalence formula E = mc^2 and his work on the photoelectric effect, for which he won the Nobel Prize in Physics in 1921. Einstein made significant contributions to the understanding of atomic and molecular structure, photoproduction, and cosmic rays. He was also known for his theoretical and experimental work on the motion of particles in a fluid, the theory of Brownian motion, and the quantum theory of radiation. Ask me anything related to these topics, and I'll do my best to provide you with accurate and insightful answers.