The phase of mitosis where chromosomes line up at the center of the cell is called metaphase.

Here's a breakdown:

* Prophase: Chromosomes condense and become visible, the nuclear envelope breaks down, and the mitotic spindle starts to form.

* Metaphase: The chromosomes line up along the metaphase plate, which is an imaginary plane in the center of the cell. The spindle fibers attach to the centromere of each chromosome.

* Anaphase: The sister chromatids separate and are pulled apart to opposite poles of the cell by the spindle fibers.

* Telophase: The chromosomes reach the poles of the cell, the nuclear envelope reforms around each set of chromosomes, and the cytoplasm divides, forming two daughter cells.

Let me know if you have any more questions!