Kirk Yeager makes bombs from the stuff found under kitchen sinks. He does it to help the FBI defend against what officials say is the next frontier for terrorists in the United States.

Ten years ago, peroxide-based bombs were mostly the work of young pranksters. But the easy-to-make yet deadly chemical cocktails were embraced in the late 1990s by Palestinian militants and homicide bombers bent on killing large groups of people.

Now, Yeager says, such explosives are considered the most likely weapon that terrorists will use against the U.S.

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"Every serious terrorist group knows about them and knows how to make them," Yeager said. The forensic scientist heads the explosives unit at the FBI's laboratory.

The bombs are made by mixing chemicals used in common household items and easily found at drugstores or hardware stores. Experts know them as TATP, short for triacetone triperoxide, and HMTD, or hexamethylene triperoxide diamine.

Recent cases of explosions or thwarted attacks with TATP or HMTD in the U.S. include:

—Millennium bomber Ahmed Ressam. He was carrying HMTD among the 124 pounds of explosives in the trunk of his car when he was arrested near the U.S.-Canadian border in December 1999.

—Richard Reid. The would-be British shoe bomber tried unsuccessfully to detonate 8 ounces of TATP hidden in his high-top sneaker during a Paris-to-Miami flight in 2001.

—University of Oklahoma homicide bomber Joel Henry Hinrichs III. He used TATP to blow himself up near a packed football stadium in October 2005.

Also, eco-terrorists and animal rights extremist groups such as Animal Liberation Front and Earth Liberation Front are believed by authorities to use peroxide-based explosives.

Yeager, 41, who helps the FBI solve bombing cases by investigating the crime scene debris, is the only U.S. official who makes TATP and similar explosives in mass quantities. His brews are used for testing and training police officers and bomb-sniffing dogs.

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