In this study, volunteers collected their own menstrual blood, which was then put in culture with rat heart cells, and spontaneously began to beat and form heart tissue sheets. While only 20% of the collected cells successfully made this conversion, this is 10-20 times the success rate seen with human embryonic stem cells.
Why do I think this is cool? Because someday, your menstrual blood may be "recycled" into new heart tissue that is entirely your own genetically. Such a tidy (genetically, medically, immunologically, ethically) solution!
(My apologies if this has been all over the news the last week...I don't do TV anymore...)