Inside the DEA's secret lab testing deadly drugs

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.