With the spreading of antigens and antibodies, macromolecular protein complexes separate out as the precipitation line which can be recognized by naked eyes in the solution. The early improvement of immunoprecipitation is to promote polymer reaction to make immune complexes separate out from the solution. Later, researchers found that using secondary antibody and immune complexes' antibody to build a net can save the step of titration experiments of primary antibody of every antigens. This methods is still in use. In 70s in 20th century, people start use solid phase reaction. They protein A fixed in staphylococcus aureus to adsorbent antibody and bind with certain antigen. With the development of science and technology, it evolves. The microspheres of protein A or G are used to separate antibody complex from antigen complex to test antigen or target protein.