 And as it's growing, what it's doing is it's killing cells. That's what a virus does when it grows. And he's looking for clumps of dead cells. And if he sees a flask that has a lot of dead cells, he's like, oh, that one. He takes the virus out of there, plucks it out, puts it into another flask with chick cells, and he's watching to see if it kills even more cells this time. And if it does, he takes it out, puts it into a flask again. And he's basically trying to get this thing to be better and better at killing cells.