And what that allows us to do in the final step is to visualize exactly where that protein is. Now, the antibody that we want to synthesize the second time around, this antibody in step number five is known as the secondary antibody. And the secondary antibody is made so that it binds onto that primary antibody that we form in step one. So once we form this secondary radioactively labeled antibody, we then mix this mixture of antibody with our polymer sheet that contains that antigen that is bound to the primary antibody. And what happens is, because this was formed to bind onto this blue primary antibody, this complex is formed. So the polymer sheet containing the antibody antigen complex is now exposed to a solution containing the radioactively labeled antibody.