Artificial intelligences aren't going to take over Earth by building a bunch of robotic fashion models to karate-chop us to death. Instead, the A.I. takeover will come from a nasty nano-tech sludge that consumes all matter in its path to recreate itself endlessly. This "gray goo" scenario has popped up in novels by Walter Jon Williams, Rudy Rucker and Greg Bear, but it hasn't yet appeared in any major movies. Here's how we would tell a Hollywood-friendly "gray goo" story.