A classic trope in horror or thrillers is technology turning against it. New science or technology is created with the best intentions but eventually becomes a threat, unforeseen to most except maybe one person who tried to warn everyone in act one.
Stem cell technology is rapidly advancing so people can cultivate their own stem cells at home. Such a product could enable all sorts of positive outcomes, like replacement organs that won’t be rejected or same-sex couples conceiving a child based on their collected genetics without the need for donor sperm or eggs.