Last week's attacks in France have raised serious questions about the reach of Islamist militant groups into Western countries.
Much of the recent attention in the U.S. has focused on the group known as the Islamic State, after it took over territory in Iraq and Syria last year and beheaded several American hostages.
But experts say Al Qaeda, and its offshoots in countries like Yemen, still pose major risks, too.
For more on this, we're joined by Andy Liepman, senior policy analyst with the RAND Corporation. He retired in 2012 as the Principal Deputy Director of the National Counterterrorism Center and worked, also, with the CIA.