Greider discovered the enzyme telomerase in 1984, when she was a graduate student of Elizabeth Blackburn at the University of California, Berkeley. Greider pioneered research on the structure of telomeres, the ends of the chromosomes. She was awarded the 2009 Nobel Prize for Physiology or Medicine, with Blackburn and Jack Szostak, for their discovery that telomeres are protected from progressive shortening by the enzyme telomerase.