Beyond routine hematoxylin-eosin histologic examinations, specialized diagnostic techniques allow examination of biopsy material for subtle morphological and functional alterations. Morphological analytic techniques (1-micron section analysis, transmission electron microscopy, x-ray probe microanalysis, and digital image analysis) and functional analytic techniques (immunofluorescence, immunohistochemistry, and molecular biologic techniques) are valuable diagnostic tools. These techniques have applications in evaluating cutaneous T-cell lymphoma and atypical lymphocytic infiltrates, vesiculobullous disorders, lupus erythematosus and collagen vascular diseases, vasculitis, poorly differentiated tumors, storage diseases, and infections.