Most animal cells display a finite lifetime when isolated and grown in a tissue culture medium that supplies necessary nutrients, salts, and vitamins. Typical vertebrate cells divide between 50 and 100 times before they fail to continue cell division and eventually die. Many theories suggest that this limited life span is related to the corresponding life cycle of the parent organism from which the cultured cells were derived.
Also recorded with a water-dipping objective at 40x magnification, this sequence contains a multi-nuclear cell in the center.