It is mainly through division that new cells are produced. Although it can be said that they are produced by old cells, this statement is still not perfect. In the cell theory of Schleiden and Wang Shi, "new cells are produced by old cells", which they describe as growing a new cell from the old nucleus or producing a new cell in the cytoplasm like crystallization, which is actually incorrect; In 1858, Wei Erxiao summarized that cell division produces new cells. His famous saying that "all cells come from pre-existing cells" is completely correct.