"Scientists Create Blood From Stem Cells"

"Scientists have used embryonic stem cells to generate blood - a feat that could eventually lead to endless supplies of type O-negative blood, a rare blood type prized by doctors for its versatility.

'We literally generated whole tubes in the lab, from scratch,' said Robert Lanza, chief science officer at Advanced Cell Technologies.

People usually require blood transfusions that match their own blood type: A mismatch can be fatal. Type O-negative can be safely transferred into anyone, but is only possessed by about 7 percent of the population, leaving supplies perpetually short."
==> Read more: http://blog.wired.com/wiredscience/2008/08/universal-blood.html