The eukaryotic cell cycle.

The relative length of the intervals differs among cells.
1 A cell spends most of its life in interphase, which
includes three stages: G1, S, and G2.
2 G1 is the interval of growth before DNA replication.
The cell’s chromosomes are unduplicated.
3 S is the time of synthesis, during which the cell
copies its DNA.
4 G2 is the interval after DNA replication and before
mitosis. The cell prepares to divide during this stage.
5 The nucleus divides during mitosis, the four stages
of which are detailed in the next section. After mitosis,
the cytoplasm may divide. The cycle begins anew, in
interphase, for each descendant cell.
6 Built-in checkpoints stop the cycle from proceeding
until certain conditions are met.