 They're moving around, and it has to have some impact on a lot of different things, you know, your musculature, your bones, and maybe your immune system. So what is going on with an immune system as far as the astronauts are concerned when they're up there? Doug, there's actually a study out this week in Nature Communications which addresses this, and it brings up a problem that we're going to have to solve before space travel becomes an everyday phenomenon. This is...