What did HeLa cells allow scientists to do for the first time?

HeLa cells are cervical cancer cells taken from an African American woman named Henrietta Lacks in 1951. The cells were taken from Ms. Lacks without her knowledge or consent while she was undergoing radiation treatments at Johns Hopkins. Ms. Lacks died from cancer less than a year after her diagnosis.
Ms. Lacks's cells were the first line of human cells to survive in a test tube. A cell biologist named Dr. George Gey was able to isolate one cell that continued to divide and divide. Typically, cells in laboratories experience preprogrammed cell death after about fifty divisions. However, Dr. Gey realized that Ms. Lacks's cells were immortal and continued to divide into perpetuity.
HeLa cells have impacted science in many ways. These immortal cells, which will divide an unlimited number of times as long as they are maintained in a suitable environment, were used by Jonas Salk to develop a vaccine for polio. They were also the first human cells to be successfully cloned, in 1953. By 2010, HeLa had been mentioned in more than sixty thousand scientific studies, and fifty million metric tons of these cells had been grown by scientists.