Based on Richard Muller's book, Physics for Future Presidents, National Geographic investigates the science behind the dangers of a high-altitude electromagnetic pulse, or HEMP. Picture an instantaneous deathblow to the vital engines that power our society, delivered by a nuclear weapon designed not to kill humans but to attack electronics. What could happen if an electromagnetic pulse surged to earth, crippling every aspect of modern society's infrastructure, including our especially vulnerable electrical grid? Beyond the remote potential for terrorists or a rogue state deploying a nuclear HEMP, most experts agree that another source of an EMP - the sun - is inevitable. Now, get a full presidential briefing to understand what could be the electronic Armageddon in one of the world's most wired countries.

They are some of the most lethal substances on earth - transmitted through food, water, the people around you or even the air you breathe. These are bioweapons, strains of bacteria and viruses that include the most feared diseases in human history. Now, imagine that you have just become the leader of your nation and new intelligence confirms that terrorists are trying to make and unleash a biological weapon in one of your cities. What are their chances for success? National Geographic reveals a surprising picture of what could happen during a biological attack by examining potential scenarios, vulnerabilities, historical instances and the steps we can take to protect ourselves from the world's most dangerous pathogens.

From Russia to Sri Lanka to the Middle East, women are increasingly turning their bodies into bombs, blowing up markets, schools and even jetliners. Who are these women and why are they dying to kill? Lisa Ling journeys to the war-torn streets of Chechnya and Israel's occupied territories for an intense and moving look at the line where hopelessness begets rage, murder fuels martyrdom and women are increasingly dying to kill.

For up to $600 a day, private security contractors in Iraq's war zone put their lives on the line to protect V.I.P.s and to transport critical supplies. Now, National Geographic travels alongside three teams on missions in the "kill zone" to reveal street rules of defense, tools for surviving ambushes and preparedness for the unexpected. Learn how specially designed vehicle armor and customized weapons help these mercenaries survive being targeted by insurgents.

Journalist Terry Anderson was kidnapped and then held prisoner by Muslim extremists for seven years. On the 20th anniversary of his eventual release, National Geographic investigates his near-death ordeal as a hostage. American Hostage reveals Terry Anderson's harrowing experience from the man himself: They beat on me. They threatened me. They would come and sit on my chest and poke guns into my neck and say, "We kill you, we kill you.'" Hear how the loneliness, boredom and feelings of total helplessness nearly drove Anderson over the edge. And hear from Anderson's fellow hostages, his family-who spent seven long years uncertain of his fate-and the man who risked everything to free him.