A fascinating article from the New York Times looks back at the past few years of research and progress into repairing heart damage with adult stem cells. "[In April 2001] stem cells from bone marrow, injected into the damaged hearts of mice, had morphed into the special cardiac muscle cells that the body cannot replace after a heart attack. ... But four years later, the treatment has yet to demonstrate whether it will fulfill its promise. ... Ten human trials of the marrow-to-heart approach have been completed in clinics around the world, all but one with positive results. But the overall degree of improvement in the patients' heart function has been modest. At the same time, the original research that provided the rationale for many of the trials has come under severe criticism from scientists."