Prophase is the stage of mitosis that follows interphase. Some scientists consider prophase the first real step of mitosis. In prophase the envelope surrounding the nucleus begins to break down and the chromatin starts to condense into chromosomes. At this point there are two identical copies of each chromosome in the cell. In addition the centrioles will begin to move to opposite poles of the cell and form spindle fibers which will later attach to the centromere of the sister chromatids. The phases that follow prophase are metaphase, anaphase, telophase and cytokinesis.