Elon Musk and other big tech names are worried that humanity will develop artificial intelligence and a threat to humanity - think self-aware killer robots that realise their best course of action is to wipe out mankind.
Or, basically, terminators.
Musk has been raising the alarm about this possibility for a while now. At an MIT event last year, he called artificial intelligence humanity's "biggest existential threat" and compared it to "summoning the demon".
Musk was one of a slew of scientists and tech leaders, including Apple co-founder Steve Wozniak and Stephen Hawking, who signed onto a letter calling for artificial intelligence research to be aimed at creating systems that "do what we want them to do", rather than, say, killing us all.