The longest part of the cell cycle is interphase. During interphase, the cell undergoes a growth phase in which it acquires energy to copy DNA. Once the DNA is copied, the cell undergoes another growth stage and acquires energy to complete cell division.
Approximately 90 percent of a cell's life is spent in interphase. The first growth phase of interphase is called G1 phase. It is immediately followed by S phase, the stage in which DNA is copied. G2 phase is the second growth phase.
Once a cell has grown to a sufficient size and has the required amount of energy, it begins to divide. The contents of the nucleus are the first to separate in a process called mitosis. Mitosis consists of four phases. During prophase, chromosomes form, and the nuclear envelope dissolves. The chromosomes move to the middle of the cell during metaphase. Copied chromosomes separate during anaphase, which is followed by telophase. In telophase, the nuclear envelopes around the two groups of chromosomes re-form.
The final stage of the cell cycle is called cytokinesis. During cytokinesis, the cell divides its cytoplasm and other organelles. Once cytokinesis is complete, two new daughter cells are formed.
Human cell division usually takes eight to 24 hours.