Albert Einstein made many contributions to science, most notably his development of the theories of special and general relativity. He also discovered the explanation for the photoelectric effect, which was vital to the later development of the theory of quantum mechanics. His formula for the equivalence of mass and energy is one of the most famous equations in science.
Einstein is most famous for his theories of special and general relativity that overturned the long-standing dominance of the ideas of Isaac Newton. Rather than seeing gravity as a force acting on a backdrop of absolute space and time, Einstein recast gravity as an expression of the geometric shape of space itself. This enabled him to make more accurate predictions than were possible with Newton's equations.
In 1921, Einstein received the Nobel Prize in Physics for his explanation of the photoelectric effect. This laid the foundation for the development of quantum physics. His equation E=mc^2 states that mass and energy are equivalent and linked by the speed of light. This discovery led to the development of nuclear energy. Toward the end of his life, Einstein devoted his energies to an unsuccessful attempt to discover a grand unified theory that would bring together all of the various aspects of physics.