Both plant and animal cells have a nucleus, which makes them eukaryotic cells.

Here's why:

* Eukaryotic cells are complex cells that have a membrane-bound nucleus containing their genetic material (DNA).

* Prokaryotic cells are simpler cells that lack a nucleus and have their DNA floating freely in the cytoplasm.

So, the presence of a nucleus is a defining characteristic of eukaryotic cells, and both plant and animal cells fall into this category.