OCCUPATION: Harvard Stem Cell Institute co-director
PREVIOUS APPEARANCES ON THE TIME 100: 1
PRO: With Obama ending an eight-year ban on federal funding for stem-cell research, Melton can push ahead even further with his lab's efforts to find cures for diseases such as diabetes and Parkinson's.
CON: As the resources for embryonic-stem-cell research grow, so does the outcry from its critics.
Next Nicholas Christakis