Max Karl Ernst Ludwig Planck was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918.Planck made many contributions to theoretical physics, but his fame rests primarily on his role as originator of the quantum theory. This theory revolutionized human understanding of atomic and subatomic processes, just as Albert Einstein’s theory of relativity revolutionized the understanding of space and time. Together they constitute the fundamental theories of 20th-century physics.