Final answer:
The nucleolus, found within the nucleus, is the specialized site for the production of ribosomal RNA, crucial for ribosome assembly.
Step-by-step explanation:
The nucleolus is the site of ribosomal RNA (rRNA) production. Located within the nucleoplasm of the nucleus of eukaryotic cells, the nucleolus is essential for the assembly of ribosomes. The rRNA synthesized here is combined with proteins to form the subunits of ribosomes, which are then exported to the cytoplasm where they engage in protein synthesis. Unlike ribosomes, which are found both attached to the endoplasmic reticulum and free within the cell's cytoplasm, the nucleolus is specifically a nuclear structure dedicated to ribosomal biogenesis.