Every year, the editors of Science huddle together and pick an outstanding scientific achievement as the Breakthrough of the Year. This year’s winner is CANCER IMMUNOTHERAPY: harnessing the immune system to battle tumors. Scientists have thought for decades that such an approach to cancer therapy should be possible, but it has been incredibly difficult to make it work. Now, many oncologists say we have turned a corner, because two different techniques are helping a subset of patients. One involves antibodies that release a brake on T cells, giving them the power to tackle tumors. Another involves genetically modifying an individual’s T cells outside the body so that they are better able to target cancer, and then reinfusing them so they can do just that.