A cell that has stopped actively preparing to divide has entered:

1. Not every cell is cycling toward division at all times. 2. Sometimes cells enter a Gap zero phase, during which they do not actively prepare to divide. 3. That state can be temporary until an external signal triggers entry into G1. 4. It can also be permanent, as in mature cardiac muscle cells and nerve cells. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 10 'Cell Reproduction', sections 10.1-10.5_