 Okay, so now he has a sample of the virus, and he's going to try to use Geraldine's virus to make the vaccine. Okay. Let's see. So... This is, like, this is crazy. It turns out making a vaccine is insane. Yeah, this is the part where I'm like, okay, demystify it. So what does he do? So the first thing he does is he puts Geraldine's mumps virus into this lab flask with a bunch of chicken embryo cells. Why?