The talk page may contain suggestions. (October 2012). The nucleolus is contained within the cell nucleus. The nucleolus (/nuːˈkliːɵləs/ ; plural nucleoli /nuːˈkliːɵlaɪ/) is the largest structure in the nucleus of eukaryotic cells, where it primarily serves as the site of ribosome synthesis and assembly.he talk page may contain suggestions. (October 2012). The nucleolus is contained within the cell nucleus. The nucleolus (/nuːˈkliːɵləs/ ; plural nucleoli /nuːˈkliːɵlaɪ/) is the largest structure in the nucleus of eukaryotic cells, where it primarily serves as the site of ribosome synthesis and assembly.