The die is cast," declared Julius Caesar as he led his legions across the Rubicon River toward Rome. Ever since, a die--a tool used to mold raw material in manufacturing--has come to symbolize irrevocable action. Once you've built or "cast" one, there's no turning back, because the tool can be used for one purpose only. But engineers have long struggled to create a "universal die" that can change to create a multitude of shapes. The latest effort is the result of a seven-year collaboration, underwritten by the Department of Defense, between aerospace giant Northrop Grumman, MIT, and North Carolina's Cyril Bath Co.