" But normal human cells—either in culture or in the human body—can’t grow indefinitely like cancer cells. They divide only a finite number of times, then stop growing and begin to die. The number of times they can divide is a specific number called the Hayflick Limit, after Leonard Hayflick, who’d published a paper in 1961 showing that normal cells reach their limit when they’ve doubled about fifty times. "

― Rebecca Skloot , The Immortal Life of Henrietta Lacks