Evaluation of crude drugs is necessary to identify them, determine quality and purity, and detect adulteration. Microscopic evaluation specifically can identify organized drugs by histological characters using reagents or stains. It involves examining parameters like stomatal number and index, vein-islet and veinlet termination numbers, palisade ratios, and presence of structures like starch grains or calcium oxalate crystals through techniques like the Lycopodium spore method. This allows determination of purity, detection of adulterants, and differentiation of similar drugs.