This is pretty cool...

"Xerox Corp. is introducing a new security technology that prints variable text invisible under normal light but that turns visible under infrared light."

"According to Xerox, each of the four color toners the company uses — cyan, magenta, yellow and black — react differently to infrared light, the company was able to come up with a combination only detectable under infrared."

Via... http://www.democratandchronicle.com/apps/pbcs.dll/article?AID=/20071004/...