J. Hanna/Weizmann InstituteImproved recipe. After 6 days of reprogramming, nearly 100% cells that lack Mbd3 (right) have become reprogrammed (yellow). Few unaltered cells (left) have made the transition, remaining red. Given the right instructions in the lab, mature cells can turn back into embryoniclike ones that researchers covet, but the process is frustratingly slow and inefficient. By removing a molecular brake, scientists have now figured out how to reprogram cells with almost 100% efficiency.In a process called cellular reprogramming, researchers increase the expression of four genes in skin, blood, or other mature cells to turn them into induced pluripotent stem...