A biopsy by Electron Microscopy (EM) is a specialized pathology test using a powerful microscope (electron beam) to examine ultra-fine tissue details (ultrastructure) beyond light microscope limits, crucial for diagnosing kidney diseases (glomerulonephritis, Alport syndrome), muscle/nerve disorders, and viral infections by revealing cell damage, viral particles, or abnormal deposits, often essential when light microscopy & immunofluorescence aren’t enough