Here's why:

* Nissl bodies are clumps of rough endoplasmic reticulum (RER) found in neurons. They are responsible for the synthesis and processing of proteins, particularly those involved in neurotransmission.

* RER is a network of interconnected membranes studded with ribosomes. It is the primary site of protein synthesis in all eukaryotic cells.

So, while Nissl bodies have a specific name and function in neurons, they are essentially the same organelle as the RER in other cells.