In the lag period, after biological seeds are inoculated into the culture medium, there is an adaptation stage to the environment. At this stage, the total amount and concentration of cells remain unchanged, that is, cells do not grow or synthesize products.

In the accelerated growth period, cells adapt to the new environment and begin to grow and reproduce, and individual differences of cells lead to the gradual increase of cells.

In exponential growth period, also known as logarithmic growth period, the number of cells will double at regular intervals.

During the growth period of meiosis, the growth and reproduction of cells cause the scarcity of nutrients, and the metabolic products have limited influence on their growth, which slows down the growth rate.

In the balanced growth period, the growth rate and death rate of cells are equal, reaching a balance.

In the negative growth period, under the joint action of nutrition and metabolites, the cell death rate is greater than the growth rate, and the cell number tends to decrease.