The nucleus of a cell stores nucleic acids known as DNA, as well as a small and densely packed bundle of nucleic acids and proteins known as the nucleolus.
Cells known as eukaryotes contain nuclei and are typically found in complex organisms. The DNA found within a nucleus is responsible for the containment and transfer of genetic material to new cells during cell division. Nuclei also serve to control a cell's biological functions such as growth and reproduction. The nucleus is protected by a layer called the nuclear envelope, which contains special pores that allow essential materials to enter and exit the nucleus to aid in the production of genetic substances.