Grey goo

Grey goo is a scary idea that scientists think might happen in the future. It is a kind of science-fiction story about tiny self-replicating robots that start to copy themselves over and over again and spread out of control. They would start to take over the world and eat up all of the resources, eventually leading to the end of the world. In real life, scientists are trying to make sure this doesn't happen by making sure that no robot could ever replicate itself.