Frank L. H. Wolfs
Department of Physics and Astronomy, University of Rochester, Slide 9
Einstein's Life:
Development of quantum theory.
Einstein received the 1921 Nobel Prize of Physics for "his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."
Quantum theory was successful in describing the motion of electrons in atoms, using wave functions to provide information about the probability to find the electrons in a particular state.
Einstein could not accept the lack of certainty.  He stated "I, at any rate, am convinced the He is not playing dice."
Image © Institut international de physique Solvay
Courtesy AIP Emilio Segr Visual Archives.