Here's why:

* The nucleolus is a specialized region within the nucleus of eukaryotic cells. It's not a membrane-bound organelle, but a densely packed area rich in RNA and proteins.

* The nucleolus is the site of rRNA synthesis. It contains the genes that code for rRNA, and the machinery to transcribe and process these genes into mature rRNA molecules.

* rRNA is a key component of ribosomes, the cellular machinery responsible for protein synthesis.

So, the nucleolus plays a vital role in the production of ribosomes by creating the rRNA component.