Most of the cells in our body are in G0 phase, when they are not dividing or preparing to divide. However, the ability of the cell to re-enter the cell cycle depends on the cell type. For example, a nerve cell, cardiac muscle cell, or a skeletal muscle cell are permanently in G0 phase and have dismantled their cell cycle control system so that they cannot re-enter the cell cycle. On the other hand, most liver cells are in G0 phase but they can re-enter the cell cycle and divide if the liver is damaged. Furthermore, lymphocytes exit and re-enter continually throughout their lifespans.