Visually, the Golgi apparatus looks like a series of flattened, disc-shaped sacs stacked one on top of the other. These flattened-sacs are in fact membrane-enclosed sacs called cisternae, and each cisternae has an inner region called the lumen which houses soluble proteins and enzymes for processing. Typically, a Golgi apparatus will have anywhere from 4 to 8 cisternae that are divided into the following regions: cis, medial, trans and the trans Golgi network (TGN). The cis region of the Golgi contains cisternae that are closest to the rough endoplasmic reticulum, and it is this area where macromolecules are received. The medial and trans-cisternae regions of the Golgi are where a majority of the biochemical modification to macromolecules occur, and the TGN is where they are packaged and transported.