Albert Einstein is famous for his theory of relativity, which changed our understanding of space, time, gravity, photoelectric effect and the universe. Einstein perfected his theory of relativity, which tried to explain how everything in the universe works. His new theory gave better predictions of planetary orbits around the sun and the explanation of how gravitational forces work. He proved the existence of atoms. Atomic theory says that any liquid is made up of molecules. He won the Nobel Prize in Physics in 1921.