Grey goo (also spelled
gray goo) is a hypothetical
end-of-the-world scenario involving
molecular nanotechnology in which out-of-control
self-replicating robots consume all matter on
Earth while building more of themselves, a scenario that has been called
ecophagy ("eating the environment", more literally "eating the habitation"). The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.