Defeating cancer is like assembling an exceedingly tricky jigsaw puzzle. We may have some ideas about the big picture, but we're left with a jumble of interior pieces to match up. Fortunately, Dr. Phil Greenberg likes puzzles. Greenberg and his colleagues focus on one major portion of this puzzle: the function of disease-fighting immune cells called T cells. He has become a world expert in discovering how T cells can be manipulated to treat a range of cancers.