Powerful painkillers can often dispatch acute pain, but using them for chronic, persistent pain carries the risk of addiction. Nearly two million Americans have a substance abuse disorder stemming from prescribed opioids. So scientists are researching ways to treat pain without drugs. Journalist Yudhijit Bhattacharjee writes about them in The National Geographic this month in "A World of Pain." Plus, University of Maryland neurobiologist Dr. Luana Collaca describes her research using virtual reality to manage chronic pain.