This news item is about: Stem cells within the heart have proven to be an elusive and controversial population. Now research scientists from Cornell’s College of Veterinary Medicine and collaborators from the University of Bonn have successfully isolated and purified mouse heart precursor cells (heart stem cells) from the developing heart, a key step in determining the specific processes that either maintain stemness or promote differentiation into vascular or cardiac fates. The demonstration that cardiovascular precursors expand and differentiate to all three heart cell types (cardiac, endothelial, and smooth muscle cells) follows recent advances by several groups who demonstrated that cardiac differentiation from embryonic stem cells occurs through the formation of a heart stem cell with the capacity to differentiate into the major cardiovascular lineages.