1. Start period. Cells have just begun to adapt to the environment, so their growth is not vigorous and their growth curve is basically flat.

2. Logarithmic period. Cells adapt to the environment, grow vigorously, grow very fast, the number of cells increases exponentially, and the growth curve rises abruptly.

3. Equilibrium period (or static period). Because the nutrients in the culture medium are limited, and the number of cells has reached a lot at this time, they compete with each other, so the number of dead cells is equal to the number of new cells, and the growth curve flattens again.

4. Apoptosis. The culture medium is exhausted, and the metabolic waste of cells accumulates, which leads to a large number of cell deaths and a sudden decline in growth curve.