The PIA-PINK staining solution is a nanoparticle of gold-conjugated anti-rabbit or anti-mouse 2nd antibodies. When the antigen-specific primary antibody (protein-specific primary antibody) is added by the user, the secondary antibodies nanoparticles bind to the freely accessible Fcγ-fragment of the user's primary antibody. The resulting hybrid forms a signaling unit that accumulates on the target protein resulting in a permanently visible signal.