Back in the '90s, when regenerative medicine was more sci-fi than reality, materials scientist Samuel Stupp had a big idea. He knew that damaged body tissue lost its ability to knit itself back together with natural biological fibers when the damage was too extensive. What if he could deploy an army of self-assembling molecules to restore the body's self-repairing powers to reverse spinal cord injuries or Alzheimer's? Since that eureka moment, Stupp, 49, has brought his vision to life. One of his many successes: making paralyzed mice walk again by injecting them with a liquid containing nanomolecules that assemble into fibers and attract new nerve cells. Stupp thinks his nanofiber approach will become the centerpiece of regenerative medicine. "We have covered the broadest range of conditions--heart disease, diabetes, Parkinson's--with a single platform," he says. "That's what makes it special."