Using stem cells from the unborn to treat adult diseases has created an anguished public debate. Now research news from Harvard Medical School scientists may help to end that debate by showing that adult stem cells can be coaxed into performing new functions. Researchers working with diabetic mice first killed cells responsible for the diabetes. The animals’ adult stem cells took over and regenerated missing cells needed to produce insulin and eliminate the disease. “It was a miracle that we didn’t expect,” says researcher Denise Faustman, the associate professor of medicine who leads the research. Setting up a trial for patients to test the technique has already begun at Massachusetts General Hospital in Boston. Perhaps one of the most interesting questions raised by the research is this: Why doesn’t the body use adult stem cells on a regular basis to heal itself? It may be because adult stem-cell populations are small and need some sort of outside stimulation.