Ribosomal RNA (rRNA) is a type of RNA that plays a crucial role in the formation of ribosomes, the cellular structures responsible for protein synthesis. It serves as a structural component of ribosomes, helping to organize the ribosomal proteins and facilitating the translation of messenger RNA (mRNA) into proteins. In eukaryotic cells, rRNA is produced in the nucleolus and combines with proteins to form the large and small subunits of ribosomes. In prokaryotes, rRNA is also essential for protein synthesis, and its sequences are highly conserved across different species, making it useful for evolutionary studies and classification.