-The G0 phase is a period in the cell cycle in which cells exist in a quiescent state. G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.
A cell that has exited from the cell cycle is in G0 phase. This phase is similar to G1 in that each chromosome consists of a single chromatid as the chromosomes have not undergone DNA replication.
A cell in G0 can remain in this phase of the cell cycle indefinitely. The difference between G1 and G0 is that a cell in G1 is actively preparing to enter S phase.
