Answer the following question given this paragraph: 

The nucleus of many cells also contains a non-membrane bound organelle called a nucleolus , shown in Figure below . The nucleolus is mainly involved in the assembly of ribosomes. Ribosomes are organelles made of protein and ribosomal RNA (rRNA), and they build cellular proteins in the cytoplasm. The function of the rRNA is to provide a way of decoding the genetic messages within another type of RNA (called mRNA), into amino acids. After being made in the nucleolus, ribosomes are exported to the cytoplasm, where they direct protein synthesis.


Q: What are organelles made of protein and ribosomal rna (rrna)?


A:
ribosomes