Scientists are making progress in using existing biochemical signalling mechanisms to induce regeneration where none would normally have happened. Via Chron.com, more on progress in nerve regrowth: "Scientists have used stem cells and a soup of nerve-friendly chemicals to not just bridge a damaged spinal cord but actually regrow the circuitry needed to move a muscle, helping partially paralyzed rats walk. ... This is an important first step, but it really is a first step, a proof of principle that you can rewire part of the nervous system ... the new research details a complex recipe of growth factors and other chemicals that entice the delicate cells to form correctly and make the right connections. Miss a single ingredient, and the cells wander aimlessly, unable to reach the muscle and make it move." These are the first steps on a very long and complex road - but progress has been very encouraging in recent years.