The endoplasmic reticulum is a series of membranes found throughout the cell that are connected to the nucleus. The endoplasmic reticulum can be smooth or rough. A smooth endoplasmic reticulum (SER) does not have ribosomes attached whereas a rough endoplasm reticulum (RER) does. The membranes of the endoplasmic reticulum form sacs called cisternae. Proteins are folded in the cisternae spaces called lumen. Additionally, the smooth endoplasmic reticulum forms lipids and steroids. When enough proteins have been created a vesicle is pinched off of the membrane. This transition vesicle then moves through the cytoplasm from the endoplasmic reticulum to the Golgi apparatus. The Golgi apparatus then packages, transports, distributes, or stores the contents of the vesicle. After the Golgi apparatus does its work on the contents of the vesicle, a secretory vesicles is created and pinched off into the cytoplasm. The contents of the secretory vesicle are delivered to where they are needed within the cell.