Health Explained: How to make stem cells
21 June 2012 Last updated at 11:49 BST
Dr Dusko Ilic, a senior lecturer in stem cell science at King's College London, shows the BBC how stem cells for research are generated from spare embryos donated by couples at the Assisted Conception Unit at Guy's Hospital, London.
He undergoes two changes of clothes to first enter the embryology laboratory, and then puts on further protective clothing to enter the stem cell laboratory where millions of stem cells are grown for use in research.
The procedures and stringent safety checks developed within the unit to generate stem cells lines are the subject of a new paper in the academic journal Nature Protocols.