Here's why:

* Eukaryotic cells are complex cells that are found in plants, animals, fungi, and protists. They are characterized by having a membrane-bound nucleus that contains their genetic material (DNA).

* Prokaryotic cells, on the other hand, are simpler cells that lack a nucleus. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

Examples of cells with a nucleus:

* Animal cells

* Plant cells

* Fungal cells

* Protozoan cells

Examples of cells without a nucleus:

* Bacteria

* Archaea