The process of centrosomes beginning to move apart in animal cells is referred to as the prophase stage of mitosis. The physical separation of the centrosomes marks the final step in the prophase stage.
The prophase stage of mitosis begins with the disappearance of the nucleoli in the nucleus. This is followed by the formation of chromosomes, which result from the coiling and condensing of chromatin fibers. These chromosomes then form pairs and join at the centromere of the cell.
Before centrosome separation, spindle fibers begin to form in the cytoplasm of the cell. When the centrosomes move apart, the spindle fibers between them lengthen. The period after centrosome movement is called the metaphase.