So I'm doing CRISPR this week. Starting with 30 million stem cells, I worked my way down to about 500,000 that survived electroporation, 2% of which actually showed a marker of Cas9 expression. Of those, maybe 10% will survive this week and grow from single cells back into full colonies without losing their pluripotency. Of those, maybe 10% will actually have a change that I want (destroying gene function). I believe it'd be an order of magnitude lower if I actually wanted to actually wanted to make a mutation in a more targeted way. So 0.0003% of my starting cells will actually be gene edited and usable afterwards. I personally only need about 10 in total to make it through the whole process, but it's hard to look at those numbers and feel we're a longgg way from designer babies.