Video of the week | The immortal cells of Henrietta Lacks

In order to test medicines, study disease and unravel the workings of human cells, scientists need material to work with. To produce results which are consistent, scientists need the cells they work with to stay same each generation - in other words, they must all be clones. Cells harvested from a tumor belonging to a woman named Henrietta Lacks proved to be the key to this problem. Known as HeLa cells, they have been instrumental in producing everything from over-the-counter drugs, to unlocking the secrets of human DNA.