Endoplasmic Reticulum:

The endoplasmic reticulum is known as the ER for short. The endoplasmic reticulum is so extensive that it often accounts for more than 50% of the cytoplasm of a cell. There are two endoplasmic reticulums, a rough endoplasmic reticulum, which contains attached ribosomes, and a smooth endoplasmic reticulum, which does not contain attached ribosomes. The rough endoplasmic reticulum gathers proteins from ribosomes creating the proteins, and sends the protein to the smooth endoplasmic reticulum, which sends the proteins to the golgi bodies to be manufactured.