Together, these two regions are known as the endoplasmic reticulum. Now, just outside the nucleus are a series of mazelike membranes called the endoplasmic reticulum, or simply the Er. And we have two types. We have the rough endoplasmic reticulum that contains these dots, and this smooth endoplasmic reticulum, shown in region five that lacks those dots. So the endoplasmic reticulum, right next to our nucleus contains ribosomes embedded in our membrane of that Er. And this gives it a granular appearance under the microscope.