A team from the University of Cambridge's Gurdon Institute created a model human embryo with a heartbeat and traces of blood. These models, I mean, how much can we really learn from them at the moment? If we've got this black box, do we know how close they are to the real thing? That's a really good question. And one interesting thing is that it will be necessary if you want to really be confident that they're replicating that process,. You do need to be able to compare them to what's happening in natural embryo.