I feel like, even though they got this knowledge, any researcher at any time could have grown hindbrain cells from pluripotent stem cells -- the resulting practice didn't _require_ the understanding. I also don't get why they needed a pluripotent stem cell and not, say, another hindbrain neuron. I get the claim that you can't get forebrain neurons to act like hindbrain neurons, but is it possible that every previous researcher who was trying to grow hindbrain neurons in vitro was starting with forebrain neurons?