Cellular structure that appears on microscopy as Òstack of pancakesÓ; serves as condensation and packaging structure for high-carbohydrate macromolecules and synthesis of lysosomes and membrane glycoproteins. ÒFormingÓ face is close to endoplasmic reticulum, and ÒmatureÓ face points toward cell surface. Best marker enzyme for this structure is glycosyl transferase.