Metaphase: Chromosomes align as a result of dynamic changes in the mitotic spindle.

Once each chromosome is attached to the mitotic spindles from both poles of the cell, the microtubules of the mitotic spindle lengthen or shorten to move the chromosomes into position in the middle of the cell. There the chromosomes are lined up in a single plane that is roughly equidistant from both poles of the cell. This stage of mitosis, when the chromosomes are aligned in the middle of the dividing cell, is called metaphase (see Fig. 11.5). It is one of the most visually distinctive stages under the microscope.