Rob Knight, co-founder of the American Gut Project at the University of Colorado in Boulder, works in the lab where the samples are processed. The American Gut Project hide caption

itoggle caption The American Gut Project

After a quick swipe and online registration, these test tubes were ready to ship back to the lab at the University of Colorado in Boulder for sequencing and analysis. Katherine Harmon Courage for NPR hide caption

itoggle caption Katherine Harmon Courage for NPR

Number of providers by state who wrote at least 3,000 prescriptions for Schedule 2 controlled substances in 2012 in Medicare Part D. ProPublica/NPR hide caption

itoggle caption ProPublica/NPR

Radiation therapy is effective in treating breast cancer but typically requires dozens of visits over five to seven weeks. A newer protocol takes just three weeks. Antonia Reeve/Science Source hide caption

itoggle caption Antonia Reeve/Science Source