Now, the next step is to take this polymer sheet and we mix it with this antibody that we form in step one. And once we mix these two mixtures, this antibody, the primary antibody, it will basically bind onto the proteins found in one of these bands because one of these bands will contain that antigen that is specific for this protein. And so let's suppose it's the second band from the top that contains the proteins that we want to study. And so this antigen or this antibody will bind to the antigen, the protein found in the second band. So the monochrome antibody is added onto the polymer sheet containing the separated protein mixture and it only binds onto the antigen, onto the protein that we actually are interested in. Now, in step number five, we synthesize yet another antibody and now we synthesize an antibody that is radioactively labeled.