Scientific American looks at work on bringing organ regeneration from lower animals to mammals like us: "Our research group has already described a natural blastema in a mouse amputation injury, and our goal within the next year is to induce a blastema where it would not normally occur. ... We hope that this line of investigation will also reveal whether, as we suspect, the blastema itself provides critical signaling that prevents fibrosis in the wound site. If we succeed in generating a blastema in a mammal, the next big hurdle for us would be coaxing the site of a digit amputation to regenerate the entire digit ... Developmental biologists are still trying to understand how joints are made naturally, so building a regenerated mouse digit, joints and all, would be a major milestone in the regeneration field. We hope to reach it in the next few years, and after that, the prospect of regenerating an entire mouse paw, and then an arm, will not seem so remote. Indeed, when we consider all that we have learned about wound healing and regeneration from studies in various animal models, the surprising conclusion is that we may be only a decade or two away from a day when we can regenerate human body parts."