Nucleus
Explanation:
In eukaryotic cell, organelles are known to be compartmentalize—membrane bound which can be double or single membrane—except the ribosome. The deoxyribonucleic acid (DNA), which holds the genetic information of all living organisms, is located in the nucleus. It is very distinct whenever you view plant or animal cells under the microscope. DNA (in the form of chromatin) can't be seen during interphase (period of DNA replication in preparation for cell division) until cell division. However, when cell divison comes, DNA (as chromatin) can now be seen as densed structure called as a chromosome.
On the other hand, prokaryotic cells have no membrane-bound organelles so their "nucleus" is called a nucleoid region where the genetic is diffused or scattered within that region.
