The Golgi complex is composed of numerous sets of smooth cisternae, which are coated with lipid membranes. Each disc-shaped cisternae forms a structure that resembles a stack of plates, called a Golgi stack. The Golgi complex contains a great number of vesicles. These vesicles are used to send molecules to the cellular membrane, where they are excreted. There are also larger secretory vesicles, which are used for selective excretion.

The Golgi is principally responsible for directing molecular traffic in the cell - nearly all molecules pass through the Golgi complex at some point in their existence. The sorting is mediated by the vesicles. When proteins bind with their appropriate receptor on the vesicle, they are encoated in the vesicle and transported away.