Mitosis is the act of cell division. It starts out with the interphase, where the cell prepares itself for division. In this phase, the DNA of the cell will be doubled. However, this is just a preparation phase and is not a real phase for the cell's division. The next phase is the Prophase. In this phase, the nuclear membrane becomes less distinct and the chromosomes become more distinct and you can see that they are connected in pairs, called centrioles. In the next step, Metaphase, microtubles assemble and form a network where the centrioles are moved on. In step 3, the Anaphase, the chromosome pairs separate and each of them go to opposite ends of the cell's equator. The nuclear membrane has completely disappeared at this stage. At the last stage, Telophase, the cell is now pinched together in the center and the nucleus is reconstructed, along with the membrane.