4.1 CELL STAGES
All cells come from preexisting cells. This is a founding principle of the cell theory and a component that has withstood scrupulous experimentation. Eukaryotic cells cycle between two prominent phases: Interphase, which is when the cell is metabolically active in preparation for eventual entrance into M Phase, which is the stage where cells divide (Figure 4.1). These phases were initially identified via microscopy, as the nucleus presents differently during each phase. However, further investigation of the chromatin, cellular metabolism, and protein synthesis led to a more complete understanding of the events associated with cell division.