And this is the intracellular domain region found on the inside portion of the cell. And this is the region that contains the tyrannine protein kinase domain that will be responsible for initiating the first phosphorylation process as we'll see in just a moment. Now, this is the Seatile, the carboxyl terminal end of this polypeptide and we'll see why that's important in just a moment. So we basically have these two identical monomers in their unbound form. They're separated because the EGF is not bound to this structure. But let's see what happens upon the binding of EGF.