Analysis: Primary cultured cells will divide. Generally, the primary cultured cells are not easy to pass down when they are passed to 10 generation, and the growth of cells is stagnant, and most cells are aging and dying. Passage culture is generally passed to 40-50 generations, and this cell transfer is called cell strain. The genetic material of cell line has not changed. Its mitotic ability is the same as that of primary culture. When the cell line reached the 50th generation, there was a "crisis" and it could not be passed on any more. However, some cells are called cell lines because their genetic material has changed and they are cancerous. The dividing ability of these cells is much stronger than that of primary culture. It has the characteristics of infinite proliferation.