What is the most traded legal item in US prisons? Instant Noodles. Celia Hatton explores the story behind instant noodles. It's a journey that starts in Japan, at the nation's instant noodle museum, and then takes her to China, still the world's number one market for "convenient noodles" as they're known there. And she hears why instant noodles have emerged as the prisoners' currency of choice.