The function of mitosis is to duplicate a cell's chromosomes; a crucial step during cell division and replication. After mitosis is complete and there are two full sets of DNA, a process called cytokinesis takes place to split the cytoplasm and rest of the cell into two identical parts.
In order for an organism to repair and grow, its cells must be able to duplicate. Most cells undergo mitosis for this to happen. There are five stages of mitosis. During the first phases, phophase and prometaphase, the chomosomes are revealed in the middle of the cell and are replicated. They are then split apart and pulled to either side of the cell in the final three phases so that cytokinesis can occur.