A screen presents the winners of the Nobel Prize in Medicine, U.S.-British scientist John O'Keefe and Norwegian husband and wife Edvard Moser and May-Britt Moser, for their discoveries of cells that constitute a positioning system in the brain. TT News Agency/Reuters/Landov hide caption

itoggle caption TT News Agency/Reuters/Landov

Molecular biologist Randy Sheckman, who shared the 2013 Nobel Prize in physiology or medicine, acknowledges applause after receiving his prize during the ceremony in Stockholm last December. Pascal Le Segretain/Getty Images hide caption

itoggle caption Pascal Le Segretain/Getty Images

Shinya Yamanaka from Kyoto University was named the winner of the Nobel Prize in Physiology or Medicine for discovering how mature, adult cells can be reprogrammed into immature stem cells. Shizuo Kambayashi/Associated Press hide caption

itoggle caption Shizuo Kambayashi/Associated Press

Dr. Ralph Steinman of Rockefeller University died Friday, three days before he was named a winner of the Nobel Prize in Physiology or Medicine for "his discovery of the dendritic cell and its role in adaptive immunity."

Mike Groll/AP hide caption

itoggle caption Mike Groll/AP