see how far the research has come. why was there this idea that injecting stem cells into the spinal cord could even help? >> yeah. so actually that's a great question, because the answer is counter intuitive. what most people think when they're talking about stem cell social security that we're going to create a cell and replace a cell in the nervous system. we're not repair or replacing motor neuron, we're trying to have them heal and grow back. >> does that mean that if you're protecting them that the patient won't get worse? >> that's exactly right. >> stem cells are located throughout our bodies. our reserve army of regeneration and repair. when we're injured or sick, stem cells will divide and create new cells. depending on where the cells are in the body, they adapt becoming specialized blood cells, muscle cells or brain cells, for example. >> it was almost as if the cells were guided missiles, like actually could detect where there's a problem and go there.