Mitosis is a special kind of cell division used by eukaryote cells. Mitosis is really a division of the nucleus into two identical nuclei. It is followed by cytokinesis which is the division of the cytoplasm into two. Just imagine for a moment.
Mitosis is essential for growth and repair.
During mitosis, one cell divides into two genetically identical cells. Before mitosis starts you cannot see any chromosomes in the nucleus, however, all the DNA in the nucleus is replicated exactly. During prophase the chromosomes coil up. They become shorter and fatter. The nuclear envelope seems to disappear.