So thrombin. And then it's this thrombin that basically goes on via the common pathway or the final common pathway to ultimately form this meshlike network of fibrin we call blood clots because thrombin activates fibrinogen into fibrin monomers and then these fibrin monomers basically aggregate. They form these clusters that form our blood clots. Now thrombin is also important because it actually goes back and creates many different positive feedback loops as we'll see in just a moment and that amplifies the effect. Now let's look at the intrinsic pathway because ultimately it's the intrinsic pathway that is affected by this medical condition we call Hemophilia A. So in the intrinsic pathway following the exposure of the surrounding tissue, following that cut in the blood vessel that basically stimulates the proteolytic activation of factor twelve.