Al's Hobby Shop in this leafy corner of suburban Chicago is always packed with mothers looking for Cub Scout badges, teenagers ogling imported slot cars and grown men playing with model trains.

But to federal law-enforcement officials, Al's is also a possible terrorist supply depot. And so, last October, a special agent from the Bureau of Alcohol, Tobacco, Firearms and Explosives was sent to Al's from Washington to buy $1,700 in model rocket motors.

"The guy told me that the government wanted to do some tests," recalls Tim Lehr, who sold the agent 40 motors containing almost 60 pounds of propellant. "He wouldn't say what the tests were for, but I could guess: The government wanted to ruin my hobby."

Since the passage of the initial post-9/11 antiterrorism laws in October 2001, hobby rocketry has been struggling to avoid regulation that enthusiasts say will destroy their sport, deter youngsters from pursuing an interest in science and waste the nation's limited law-enforcement resources. The Department of Justice says that federal agents need to keep an eye on who is buying model rockets because the toys are potentially dangerous and could be adapted by terrorists to attack airplanes and American soldiers.

The comb, that simple device millions of people pass through their hair every day, could become the latest tool in the battle against terrorism.

That’s because a group of University of Rhode Island researchers has found that chemicals used to make bombs remain in the hair of explosives handlers long after repeated washings.

The lead researcher, Professor of Chemistry Jimmie Oxley, one of the co-directors of URI's Forensic Science Partnership, has also found that when the research team members attached ordinary gauze to combs, they had effective collection devices.

Ultimately, fighting the war on terrorism may have less to do with giant aircraft carriers and more to do with atomic-scale detection and prevention systems. Nanotechnology, which is expected to transform everything from computer processors to drug delivery systems, may also be the key to homeland security, argues a new book.

In Nanotechnology and Homeland Security: New Weapons for New Wars (Prentice Hall, 2003), Mark A. Ratner, a professor of chemistry at Northwestern University and a noted expert in molecular electronics, and his son Daniel Ratner, a high-tech entrepreneur, claim that current research in nanotechnology will lead to intelligent sensors, smart materials, and other methods for thwarting biological and chemical attacks.