The cell cycle is the sequence of events in a cell that culminate in cell division.

Interphase

When a cell is not in the process of dividing, it is in a phase known as interphase.

During interphase, which is the longest part of the cell cycle, the cell is preparing to divide.

In eukaryotic cells - a eukaryotic cell has a nucleus; cells without nuclei are known as prokaryotic cells - interphase can broken down into three shorter stages:

1. G₁ (Gap 1)
2. S (Synthesis)
3. G₂ (Gap 2)

Chromosomes are duplicated during the S phase, in preparation for cell division.

During the G₁ and G₂ phases, cells grow and are metabolically active, but chromosomes are not replicated.

Mitotic phase

After the G₂ phase, interphase ends and the cell enters the M (Mitotic) phase.

The M phase consists of two stages:

1. Mitosis - The nucleus splits to form two new nuclei, each with identical sets of chromosomes.
2. Cytokinesis - The whole cell divides in half, so two new cells are created.

G₀ Phase

If a cell does not receive enough nutrients, it will enter a G₀ phase.  This is a stationery phase, in which the cell cycle stops and the cell does not grow or divide.

When nutrients are replenished, the cell cycle will resume.

The G₀ phase is an important part of the cell cycle in multicellular organisms.

If all of the cells in a multicellular creature had to grow and reproduce constantly, some types of cells would become too prolific.

Cells in multicellular organisms are usually in the G₀ phase.

Once they have reached maturity, human muscle cells and human nerve cells remain in the G₀ phase all the time.

The length of the cell cycle, and the proportion of time spent in each phase of the cycle, is different for different kinds of eukaryotic cells.