The endoplasmic reticulum (sometimes abbreviated the E.R.) is an organelle in the cell that has passageways that assist in carrying proteins and other materials throughout the cell. The E.R. also sometimes will package materials similar to the golgi body to send throughout the cell. Think of the E.R. as a highway in the cell that materials can use to move from one place to another. The E.R. works in close conjunction with ribosomes and the golgi body. Sometimes ribosomes which look like little bumps will be directly attached to the E.R. and when this happens it is called the “rough endoplasmic reticulum”. When there are no ribosomes attached to the E.R. it is called the “smooth endoplasmic reticulum”.