Firstly an extensive summary of the diagnostic power and limits in renal glomerular pathology of light microscopy even corroborated by all the special histochemical stains is made. Secondly a complete list of all those renal glomerular diseases in which electron microscopy is unanimously considered necessary for the diagnosis is given as well as the main and most updated references pertinent to those rare and recently recognized pathological entities in which EM proved as a fundamental diagnostic tool are provided. Thirdly the authors focus on the importance of immunohistochemistry (IIC) in the diagnosis of immune-mediated renal glomerular diseases. The advantages and disadvantages of immunofluorescence microscopy (IF) and immunoperoxidase method (I-perox) are respectively discussed. The value of I-perox staining method applied to sections from paraffin blocks is emphasized and some technical suggestions in order to optimize results are given. Among the latter the choice of the used fixative for the purpose of preserving antigenicity of immunoglobulins and complement fractions, the timing of tissue fixation as well as the quantitation of enzymatic pretreatment relative to the duration of fixation, and the repeated washings with phosphate-buffer saline to minimize background staining. Ultimately the authors report on their preliminary personal results with the use of I-perox staining on sections from paraffin embedded renal core biopsies. Although if is their favourite diagnostic microscopy for evaluating renal immunopathology the authors underline I-perox method as a helpful tool to rely on at least in those circumstances when frozen material for IF is not available due to the scarcity of core biopsy, when glomeruli are absent in frozen sections, or when due to a technical lab accident the frozen tissue devoted to IF has been ruined or lost, and the only available material is the one which lies embedded in paraffin. The LSAB ("labelled streptavidin biotin") complex and PAP ("peroxidase-antiperoxidase") working procedures are provided in detail.