Grey Goo

Grey goo (alternatively 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 known as ecophagy ("eating the environment").

Self-replicating machines of the macroscopic variety were originally described by mathematician John von Neumann, and are sometimes referred to as von Neumann machines. The term grey goo was coined by nanotechnology pioneer Eric Drexler in his 1986 book Engines of Creation, stating that "We cannot afford certain types of accidents." In 2004 he stated "I wish I had never used the term 'grey goo'."