A cleavage furrow forms during cytokinesis, which is the final stage of cell division after mitosis is complete.

Here's a breakdown:

* Mitosis is the process of nuclear division, where the chromosomes are duplicated and separated into two identical sets.

* Cytokinesis is the process of cytoplasmic division, where the cell physically splits into two daughter cells.

The cleavage furrow is a groove that appears on the cell surface during cytokinesis, eventually pinching the cell in two. It's formed by a ring of microfilaments made of the protein actin, which contracts and pulls the cell membrane inward.

So, while the formation of the cleavage furrow happens after mitosis is completed, it's essential for the successful completion of cell division.