The cell cycle has two parts, interphase and M phase. M phase is one of cell division -- it splits one cell into two cells. It is how organisms grow, maintain their health, and reproduce. The processes of cell division are also the main way of introducing the genetic variability that allows adaptation and evolution to occur.

In all cells, cell division is basically a three-step process: replication of genetic material, segregation of the duplicates, and division of the cytoplasm (cytokinesis).

In prokaryotes, a relatively simple process of cell division occurs called binary fission.

Cell division in eukaryotes requires more elaborate chemical and physical mechanisms to apportion all of the chromosomes, organelles, and other contents of the original cell into the two new cells. The primary effort is spent on passing along an accurate and functional, though not always identical, set of chromosomes. There are two types of eukaryotic cell division, mitosis and meiosis.

Binary Fission
In single-celled prokaryotes like bacteria, cell division is also reproduction. These organisms generally have a single loop of DNA, which is attached to the cell membrane. To accomplish cell division, the DNA replicates to form two loops, each one attached to the membrane at a different place. The cell wall then elongates, growing most rapidly at the segment in between the two points of attachment. This draws the chromosomes further and further apart. At this point, the membrane in between pinches inward, splitting the cell into two.

Binary fission is an efficient and rapid process, and often leads to an exponential growth in population size. Under favorable environmental conditions, bacteria can undergo binary fission every 20 minutes.

Mitosis
Mitosis is cell division that is used by eukaryotes primarily for growth, replacement, and repair. In some organisms, mitosis can also produce new organisms by processes such as budding or vegetative propagation.

Prior to the beginning of mitosis, the cell’s DNA is replicated during interphase. If replication was successful, mitosis will occur. During mitosis, microtubles extend from opposite poles of the cell, attach to each duplicated chromosome, and pull it apart. Once the sister chromatids are separated, cytokinesis splits the single cell in two.

All of the cells produced from mitotic divisions are the same; they have the same genetic information, and the same chromosome number as the cell in which division began.

Meiosis
Meiosis is cell division specifically for the production of sex cells, also known as gametes, germ cells, or as eggs and sperm cells.
As in mitosis, DNA duplication occurs in interphase, before the M phase begins. During cell division, segregation followed by cytokinesis then separates the duplicates into new cells. But unlike mitosis, meiosis includes extra steps that reduce the number of chromosomes in the resultant cells by half.

In eukaryotes, chromosomes exist in homologous pairs, one from the female parent and one from the male. During the first stage of meiosis, the members of each pair are split into separate cells. During the second stage, the sister chromatids that make up each duplicated chromosome are then segregated.

The process of meiosis produces gametes that have half of the genetic information as the original cell and no paired chromosomes. When two gametes fuse, the zygote they form has the full set of chromosomes, one pair from each parent.

Cytokinesis

Cytokinesis is the final step of cell division. It is the divison of all non-DNA cell components and the formation of a physical barrier between the new cells.

In bacterial and animal cells, a contractile ring forms in the middle of the cell and anchors itself to the plasma membrane. The ring then constricts, eventually cutting the cell in half. During cytokinesis, plants build a cell plate down the middle of the cell. When the plate spans the entire distance from cell wall to cell wall, two separate cells are created.