Given the right cues, our stem cells are capable of far greater feats of healing than take place naturally. Scientists are searching tirelessly for the controlling signals that can put stem cells to work without the risk of cancerous growth. Via ScienceDaily: "researchers screened about 147,000 molecules to find one that could transform human blood stem cells into a form resembling immature heart cells. When they implanted blood stem cells activated by this compound into injured rodent hearts, the human cells took root and improved the animals' heart function. .. Despite medical advances in treating and preventing heart attacks, once the heart is damaged it cannot repair itself ... After a week, the function of the rats' hearts had significantly improved, and after three weeks, the organs contracted as strongly as they did before the damage. Tests showed that the human cells were alive and had incorporated themselves into the heart tissue ... this drug can act on blood stem cells that are already being used in other clinical trials. This may speed its movement into clinical trials for heart repair." Note that screening 147,000 molecules for the one you want is an unremarkable feat these days - biotechnology continues to accelerate, leading to a rate of analysis and progress that would have been impossible 20 years ago.