Niels Bohr discovered that the energy levels of electrons distinct and that they revolve in orbits around the nucleus. Additionally, he discovered that the electrons could jump from one orbit to another.
Bohr's discovery led to advances in science including research on nuclear fission. This resulted in the development of the liquid droplet theory. Bohr won the Nobel Prize in Physics in 1922 due to his work.
Bohr offered refuge to German Jewish physicists who were trying to escape Adolph Hitler. His family eventually ended up fleeing Europe. He ended up in the United States where he began work with the Manhattan Project.