The Golgi apparatus is found in most eukaryotic cells. It is an organelle which packages proteins intracellularly before they are transported elsewhere. How this occurs is still under investigation. Vesicles that leave the rough endoplasmic reticulum travel to the cis face of the Golgi apparatus. They fuse to the Golgi membrane and their contents are entered into the lumen--the inside space of this organelle. The molecules are modified for transport. It is thought that the cisternae of the Golgi apparatus are built at the cis face and broken down at the trans face. When ER vesicles fuse together, this forms a cisterna at the cis face. They then move toward the trans face. From here, this is the exit face where vesicles leave the Golgi apparatus and move to targets--either inside or outside the cell. There is evidence that has been gathered while watching Golgi compartments maturing which supports the Cisternal Maturation model.