The US Drug Enforcement Administration seized over 50 million fake prescription pills and more than 10,000 pounds of fentanyl last year. CNN's Dr. Sanjay Gupta goes inside the DEA's secret lab where they are uncovering these deadly doses. For more on the opioid epidemic, watch the CNN Film "American Pain" this Sunday at 9 p.m. ET.

Sitting among the warehouses of Dulles, Virginia, is one of the US Drug Enforcement Administration's forensic labs. It's one of eight across the country where scientists analyze illegal drugs and try to stay ahead of what's driving deadly overdoses.