the g0 phase (called the g zero phase) or resting phase is a period in the cell cycle in which cells are inactive. cells enter g0 phase from g1 and stop dividing. some cells, such as neurons, remain in g0 for indefinite period. some cells enter g0 phase semi-permanently, such as some cells of the liver and kidney. many cells do not enter g0 and continue to divide throughout an organism's life, e.g. epithelial cells.