The cell cycle is a cycle which alternates between the resting stage or interphase and when the cell is actively dividing, or the mitotic phase. During interphase, the cell will grow to its full potential. It will carry out life functions and will copy the chromosomes in the nucleus. These replicated chromosomes insure that the two daughter cells that will result from mitosis, each have a full complement of chromosomes. During mitosis, the nuclear membrane disappears, and the chromatids (doubled chromosomes) attach to the spindle fibers by their centromeres. They line up in the middle of the cell, and migrate to opposite poles. Eventually, the nuclear membrane reforms around each set of chromosomes and the cell membrane pinches in half in animal cells forming two separate daughter cells. They are identical genetically, although half the size as the parent cell. In plant cells, a cell plate divides the two daughter cells. They will each enter interphase again, and the cycle will continue.