Early prophase: chromatin coils to form chromosomes, nuclear membrane disappears, and centrioles migrate to opposite poles of the cell.   Middle prophase: spindle fibers, microtubules of protein, begin developing.   Polar fibers extend across the cell from centriole to centriole.   Kinetochore fibers extend from the centromeres of a chromosome to the centrioles.   Late prophase: protein fibers called asters radiate from each centriole in animal cells.
	Kinetochore fibers move the chromosomes to the equator of the cell.
	The centromere of each pair of chromatids divides, the chromatids separate and are pushed to opposite poles of the cell by the combined efforts of the spindle fibers.   This movement is done in one quick motion.
	All spindle fibers disappear, chromatids unwind and stretch to form chromatin, and a nuclear membrane forms around each mass of chromatin.
In any fast growing tissue, cells will be found in all phases of the cell cycle. This is a picture of the very fast growing tissue of an onion root tip. Notice the different size of the cells and the obvious mitosis phases.