German physicist Dr. Maria Goeppert Mayer made groundbreaking discoveries about nuclear structure. In 1930, she moved to the US, working voluntarily around universities to research quantum mechanics. While studying the origin of the elements, she realized that nuclei with a certain number of protons or neutrons were very stable. This led her to propose a nuclear shell structure similar to the electron shell model. After writing a book on the shell model with Hans Jensen, she won the Nobel Prize in 1963.