Hayflick limit refers to the limit of normal somatic cell division times in vertebrates. This phenomenon is called "hayflick limit" (that is, the limit of cell division is 40 ~ 60 times. ) 196 1 year, American biologist Hayflick finished a paper and reported the results of their in vitro culture of human embryonic fibroblasts. Hayflick's method is to put the cells in a Petri dish and let them divide and grow until the Petri dish is full. After the Petri dish is covered with a layer of cells, normal cells will stop proliferating. Then, a small number of cells were transferred to another fresh Petri dish for culture. Hayflick found that fibroblasts could not proliferate indefinitely even under the most suitable culture conditions, but stopped after about 50 generations of division. Now research has confirmed that every animal has its own "limit". For example, a turtle can live 90 to 125 times and live to 175 years old. The more generations of cell culture, the longer the life span of animals, and vice versa. In modern gerontology, Haverick limit has been called a basic law, and cells not only follow this law in vitro, but also in vivo.