HeLa cells are a type of immortalized cell line used in scientific research, derived from cervical cancer cells taken from Henrietta Lacks in 1951. They are called "immortal" because they can divide an unlimited number of times in a laboratory cell culture plate, as long as fundamental cell survival conditions are met. HeLa cells are one of the most commonly used human cell lines in research and have contributed to many medical breakthroughs, including the development of polio and COVID-19 vaccines, the study of leukemia, the AIDS virus, and cancer worldwide. They have also been used to study the potential treatment benefits of a drug called Hydroxyurea against certain blood cancers and sickle cell anemia. Although many other cell lines are in use today, HeLa cells have supported advances in most fields of medical research in the years since they were isolated. However, HeLa cells are sometimes difficult to control, as they adapt to growth in tissue culture plates and invade and outcompete other cell lines. Through improper maintenance, they have been known to contaminate other cell cultures in the same laboratory, interfering with biological research and forcing researchers to declare many results invalid.