First the chromosomes condense and the centrioles form and spindles project from them. This is the prophase. The nuclear membrane breaks down and the spindle attaches to the chromosome. Then the chromosomes line up down the midline of the cell- this is the metaphase. The spindle shorten and the sister chromatids are pulled to the opposite poles, this is the anaphase. The nuclear envelope then reforms during the telophase and the cell splits as cytokinesis occurs.