The endoplasmic reticulum, or ER, is a cell part that makes and moves things like proteins and fats. It comes in two types:

• Rough ER: This type has bumps called ribosomes on it. It makes and sorts proteins.

• Smooth ER: This type has no bumps. It makes fats and helps clean up the cell.

The ER is connected to the nucleus, the control center of the cell. The outer part of the nucleus is directly attached to the rough ER, which helps them work together to make and move materials.