Researchers at the University of Michigan have developed an iridescent material that reveals hidden words or images in the right setting. What exactly causes the message to show? A single breath. That's right, breathing on the plastic sheets makes whatever has been inscribed on it visible -- thanks to a little instant humidity -- but otherwise hidden from view. Images are created using a custom ink-jet printer to output a water-repellant coating in the desired shape. When breathed on, water condenses to show the image -- similar to the manner in which a peacock's feathers lose their glimmer when they're wet. The group aims for the material to be used to combat counterfeiters, replacing holograms on passports and more.