In all eukaryotes, each cisternal stack has a "cis" entry face and a "trans" exit face. These faces are characterized by unique morphology and biochemistry. Within individual stacks are assortments of enzymes responsible for selectively modifying protein cargo. These modifications influence the fate of the protein. The compartmentalization of the Golgi apparatus is advantageous for separating enzymes, thereby maintaining consecutive and selective processing steps: enzymes catalyzing early modifications are gathered in the "cis" face cisternae, and enzymes catalyzing later modifications are found in "trans" face cisternae of the Golgi stacks.