evidence: Today, these incredible cells — nicknamed "HeLa" cells, from the first two letters of her first and last names — are used to study the effects of toxins, drugs, hormones and viruses on the growth of cancer cells without experimenting on humans. They have been used to test the effects of radiation and poisons, to study the human genome, to learn more about how viruses work, and played a crucial role in the development of the polio and COVID-19 vaccines.