Doctors who suspect a patient has Alzheimer's must test the person for many other physical problems first.

VOA: special.2009.09.15

For the first time, scientists around the world had a limitless number of cells they could use to test the effects of diseases, medicines and chemicals.

VOA: special.2010.07.21

Jonas Salk used these HeLa cells to test the first vaccine for polio.

VOA: special.2010.07.21