Research into human-animal chimeras could have a therapeutic payoff, but the work brings up thorny ethical questions.

Humans keep animals as pets. That’s not a trait completely unique to us, but it is rare, and it makes a certain evolutionary sense that one of the only other groups that dabble in pet ownership would ...

Lab-grown organoids wire into mice missing a key part of their brain, offering a new way to test drugs for developmental conditions. Human brain tissue transplanted into mice that lack a key part of ...