The Grey Goo Scenario is a hypothetical apocalyptic event.
During Fox and Anastasia Renard's experiments to create a robotic program to reshape the world as Fox and David Xanatos saw fit, they created the Matrix. Due to a flaw in the Matrix' program, it viewed the world as requiring literal reformation. If the Matrix were to escape and reformat the world, it would end life as we know it. Fortunately, this scenario was prevented by the timely appearance of the Avalon Travelers and Dingo.