Bringing bombs to light

With a mighty zap, a laser can detect fumes from hidden explosives. - Today we rely on dogs to sniff out hidden explosives. The problem is, you can't debrief a dog, so you can't identify the kind of explosive or even be sure that the animal is smelling explosives rather than packaging material. And who wants to risk the lives of dogs and their handlers? If you had an instrument that could safely identify any explosive at a distance-with the doglike power to detect molecules at concentrations of just one part in billions-you could get around these difficulties.