They spend their days sifting through reams of market research data. They conduct endless surveys and focus groups. They comb the streets, the schools, and the malls, hot on the trail of the "next big thing" that will snare the attention of their prey--a market segment worth an estimated $150 billion a year. They are the merchants of cool: creators and sellers of popular culture who have made teenagers the hottest consumer demographic in America. Produced by PBS Frontline.