The endoplasmic reticulum (ER) is a network of membranes found in the cells of living organisms. It plays a crucial role in the production and processing of proteins and lipids. There are two types of ER: the rough ER, which has ribosomes on its surface and helps in protein synthesis, and the smooth ER, which is involved in lipid production and detoxification. The ER is essential for maintaining the cell's health and function. It works closely with other organelles, such as the Golgi apparatus, to transport and modify proteins. Without the endoplasmic reticulum, cells would struggle to produce the materials they need to survive.