Women still take most of the responsibility for contraception, but a long anticipated "male pill" could soon become a reality. Several non-hormonal male contraceptive pills that work by slowing sperm are under development, with one entering human trials. Head of the Reproductive Medicine Group at the University of Dundee Professor Chris Barratt has dedicated his career to understanding male infertility, human spermatozoa and sperm-egg interaction. He joins us to explain how these new pills work and why it's taken so long to get to this point.