We spend a third of our lives doing it. Going without it will kill you faster than going without food. It has led to some of the seminal moments of human creativity. Sleep is vital to our existence, yet scientists know very little about it. Ken Arnold joins James Randerson and the Science Weekly team to talk about the Wellcome Collection's new exhibition of sleep and dreaming.
(Dreamy harpsichord sound effect, some rights reserved)
Is the bitter argument over human cloning coming to an end? Two research teams reported last week that they had created so-called human pluripotent stem cells - cells that can be transformed into any tissue in the body - without using embryos. Harry Moore, professor of reproductive medicine at the University of Sheffield, explains why the development is so significant.
We also feature the Guardian's investigation into two unlicensed internet companies that provide fresh sperm to women who do not have a partner and want to conceive. Prof Allan Pacey, secretary of the British Fertility Society tells us why the service could put women at risk.
Plus we sift through your thoughts on homeopathy and ask whether Nellie the elephant should be allowed to pack her trunk and say goodbye to the circus...
