An FBI Special Agent Bomb Technician prepares a homemade explosive during a National Improvised Explosive Familiarization course at Ellsworth Air Force Base, S.D., July 12, 2017. FBI Instructors led the three-day, joint exercise inside a classroom as well as in the field, detonating the explosives made and explaining the science behind each combination. (U.S. Air Force photo by Airman 1st Class Randahl J. Jenson)