And so I've labeled 123-4567. So let's basically see what each one of these steps actually involves. And let's begin with step number one. So once we phosphorylate this section, what happens is an important protein, basically known as GRB Two, actually binds onto a phosphoryl group. So a phosphorylated tyrosine residue found on this section here. So this serves as an attachment point for this GRB Two, where by the way, GRB stands for growth Factor Receptor bound Protein Two.