So we take the green mixture of antibodies. We reacted with the polymer sheet that contains the blue antibody bound onto the protein found on this second band. Now, the radioactive antibody will only bind to this band and not the other bands because only this second band contains this protein, the antibody bound onto the antigen because this was built specifically to bind onto this primary blue antibody. Now, in the final step, we basically take an Xray film. We expose it to Xrays. And what that allows us to do is allows us to visualize exactly where this radioactively labeled antibody has bound to.