Mitosis actually doesn't begin in a specific organelle. It's a process that occurs within the nucleus of a eukaryotic cell.

Here's why:

* Nucleus: The nucleus houses the cell's genetic material (DNA), which is organized into chromosomes. Mitosis is the process of dividing these chromosomes equally into two daughter cells.

* Organelles: Organelles are specialized structures within the cell that have specific functions. While organelles play roles in cell division (like the centrosomes that help organize microtubules), they don't initiate the process of mitosis.

So, while mitosis is centered in the nucleus, it's a process that involves the coordination of many cellular components.