RFID is a proven technology that's been around since the Second World War. Up to now, it's been too expensive and too limited to be practical for many commercial applications. Only recently has it attracted a great deal of attention. But if tags can be made cheaply enough, they can solve many of the problems associated with bar codes. Radio waves travel through most non-metallic materials, so they can be embedded in packaging or encased in protective plastic for weather-proofing and greater durability. And tags have microchips that can store a unique serial number for every product manufactured around the world.