The region inside a cell except the nucleus is called the cytoplasm.

Here's a breakdown:

* Cytoplasm: This is the gel-like substance that fills the cell and surrounds the nucleus. It contains all the cell's organelles (except the nucleus) and is the site of many important cellular processes.

* Nucleus: This is the control center of the cell, containing the cell's genetic material (DNA).

So, the cytoplasm is everything within the cell membrane *except* the nucleus.