Here's why:

* Eukaryotic cells are complex cells that have a membrane-bound nucleus where their DNA is housed. This includes cells from animals, plants, fungi, and protists.

* Prokaryotic cells, like bacteria and archaea, are simpler cells that lack a nucleus. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

So, any cell with a nucleus will have its DNA within that nucleus.