Mitosis begins as the long threads of DNA in the nucleus start to coil. Having already replicated these threads emerge as the double strands we know as chromosomes. Meanwhile, protein fibers grow from the migrating centrioles, forming a lattice work of spindles. For recent scientists don't fully understand, the nuclear membrane suddenly disintegrates. With amazing accuracy, a spindle from each centriole attaches itself to each of the chromosomes. Assisted by the protein fibers, the chromosomes move center stage. In a microscopic tug of war, the spindles pull each chromatid toward opposite poles. Other spindles push against each other in a ratcheting action that stretches the cell. The chromosomes then unwind and the nuclear membrane's reform. With mitosis complete, the nuclei and cytoplasm separate, creating two new cells in this ongoing cycle that sustains all life.