In eukaryotes, organisms that have nuclei, ribosomes are produced within the nucleolus of a cell. The nucleolus is located within the cell's nucleus, where most of a cell's genetic information is stored.
Ribosomes are cell organelles that are responsible for making proteins out of amino acids. Organisms need proteins to carry out life functions, such as growth and repair. Therefore, a tremendous number of ribosomes are sometimes required. For example, when mammal cells grow, they hold anywhere from 5 million to 10 million ribosomes. Each time a cell divides, the material inside, including the ribosomes, must be duplicated. The nucleolus, therefore, is often busy manufacturing ribosomes.