These protective proteins we call antibodies. And our body manufactures these antibodies so that they bind to specific types of molecules we call antigens. So for every antigen, we have a specific type of antibody that can bind to that antigen and that antigen alone. Another example is the DNA polymerase molecule. So DNA polymerase is basically this enzyme complex that only binds to specific sequence of nucleotides on our DNA. And once the binding takes place, once the enzyme binds onto our DNA, that initiates the process of DNA replication.