The technique immunoelectron microscopy uses antibodies to detect the intracellular location of structures of particular proteins at high resolution by electron microscopy. 

Antibodies against the required antigen are labeled with gold particles and then applied to ultrathin sections, which are then examined in the transmission electron microscope.

Antibodies labeled with gold particles of different diameters enable two or more proteins to be studied simultaneously.

The difficulty with this technique is in staining the ultrathin section adequately, as few molecules of antigen are present in each section.