Cell cycle is the series of events in which cells replicate and make two new cells. Cell cycle consists of stages- $G_1, S, G_2$, and $M$ (karyokinesis). $\mathrm{G}_1$ is the stage where the cell is preparing to divide. It then moves into the $S$ phase where the cell copies all the DNA. S stands for synthesis phase of DNA. Histone proteins are also synthesised during the phase. After the DNA is copied and there's a complete extra set of all the genetic material, the cell moves into the $\mathrm{G}_2$ stage, where it organizes and condenses the genetic material, or starts to condense the genetic material, and prepares to divide.