(1885 - 1962) One of the foremost scientists of the 20th century, Bohr was the first to apply the quantum theory to the problem of atomic and molecular structure. He was a guiding spirit and major contributor to the development of quantum physics; leader of the renowned Copenhagen School which struggled to work out a consistent materialist understanding of physical science during the unfolding of quantum and relativistic discoveries, Bohr maintained a long dialogue with Einstein over the meaning of these developments, and is responsible for the Correspondence Principle, one of the most important concepts for the understanding of the relation between quantum events and experience in the "macro-world".