I have always been fascinated by the story of Henrietta Lacks.
Henrietta was an African American woman from Baltimore who died of cervical cancer in 1951. Before she died some of her cancerous tissue was taken - without her permission - and the cells have been reproducing in laboratories around the world ever since.
Henrietta Lacks' cells are immortal. They are known as the HeLa cell line, and they have become deeply involved in all sorts of medical and genetic research - sometimes in the most unexpected ways.
Back in 1997 I made a film for the BBC - called The Way of All Flesh - which told the story of Henrietta and her cells.
A new book about Henrietta Lacks has just been published, and it has become a best-seller in America. And Oprah Winfrey is planning to make a film about it.
I thought I would put the film up as a background to the history and the sciences involved.
It is a really odd story - and the film also has in it members of Henrietta's family including the wonderful Deborah Lacks who is Henrietta's daughter.