Immunostaining, or immunohistochemistry (IHC) is a widely used technique to detect the presence of a specific protein in tumor tissues for in vivo mouse experiment. Here we provide some immunohistochemical protocols that are mostly used in biomedical researches. Before you harvest tissues, make sure you have the right protocols to detect the target protein you want, because some proteins can only be detected on frozen sections while others only on paraffin sections. Don't make mistakes to waste your precious tissues and time.