What is called the quiescent stage? Give information.

(N/A) $\Rightarrow$ Some cells in adult animals do not appear to exhibit division (e.g.,heart cells,nerve cells),and many other cells divide only occasionally as needed to replace cells lost due to injury or cell death.
$\Rightarrow$ These cells that do not divide further exit the $G_{1}$ phase to enter an inactive stage called the quiescent stage $(G_{0})$ of the cell cycle.
$\Rightarrow$ Cells in this stage remain metabolically active but no longer proliferate unless called upon to do so,depending on the requirements of the organism.
$\Rightarrow$ Note: In animals,mitotic cell division is only seen in diploid somatic cells. Plants can show mitotic divisions in both haploid $(n)$ and diploid $(2n)$ cells.