Within the next 15 years, we may not need to rely on the good will of blood donors. In pioneering work being carried out in Scotland into the manufacture of blood on demand, lives could be transformed. Pennie Latin meets Dr Jo Mountford of Glasgow University who is researching the manufacture of blood from embroynic stem cells, Professor Marc Turner of the Scottish National Blood Transfusion Service and Trina who suffers from a rare blood disorder called thalassemia and relies on regular blood transfusions.