Cell cycle:

The life of a eukaryotic cell can be described as a cell cycle that is described in the figure. Mitosis and cell division occur in the M phase that lasts for only about 1 h. This is followed through the G₁ phase where G stand for gap, then the S phase S stand for synthesis, during that time the chromosomal DNA is replicated and at last the G₂ phase in that the cells prepare for mitosis. Eukaryotic cells in culture classically have cell cycle times of 16-24 h but the cell cycle time can be much longer than > 100 days for some cells in a multicellular organism. Many of the variation in cell cycle times occur through differences in the length of the G₁   phase.  Some cells in vivo like neurons, stop dividing completely and are said to be quiescent locked in a G₀ phase.