Hi, I have a question concerning fluorescence microscopy and the use of antibodies to stain cells. I am a little confused about the acutal procedure. That is, I don't know where the antigen and the antibodies come from. Are they introduced by the experimenter, or are they naturally occuring in the cell? I know that the secondary antibody must be introduced by a person since it has the fluorescent tags on it, but I am confused about how it binds to another antibody. If someone could just lay out the steps in the staining process in great detail, that would be a big help. I hope I presented a somewhat coherent question. I am materials scientist who is trying to become more familiar with the bio world, so perhaps my understanding seems very deficient. In any case, assistance would be appreciated! Thanks in advance.