The cell enters the first phase of mitosis: prophase. The replicated chromosomes condense into shapes that resemble the letter X. The membrane around the nucleus starts to break down. Special structures called spindle fibers form
From there, the cell enters metaphase—the second phase of mitosis. Each chromosome attaches to a spindle fiber at its centromere (the middle of the chromosome). Chromosomes line up at the center of the cell. The next step is anaphase.
The last step is when the cell enters the last phase of mitosis—telophase. The chromosomes begin to uncoil and form chromatin. The spindle breaks down, and two new nuclei form. The cell membrane begins to close in, starting to split the cell into two.