Niels Bohr was born on October 7, 1885 in Copenhagen.
In 1920, Bohr became the director of the Insitute of Theoretical physics at the University of Copenhagen.
Bohr applied Planck's hypothesis of energy quantization to atoms and explained the spectral lines with his model of the atom. He gave a relation between classical physics and quantum mechanics by his Correspondence Principle. He developed the Copenhagen Interpretation of quantum mechanics together with Heisenberg. He also worked on nuclear physics.