Complex sentence: Rolf's work at the Rockefeller Institute later became her PhD at Columbia University which she obtained in biochemistry from Columbia's College of Physicians and Surgeons in 1920.
Split into simpler sentences: Rolf's work at the Rockefeller Institute later became her Ph.D. at Columbia University. She obtained her Ph.D. in biochemistry from Columbia's College of Physicians and Surgeons in 1920.