The placenta is indeed a miraculous organ. Not only does it provide nutrition to the developing embryo and fetus in the form of amino acids and glucose, but it also acts as an organ of respiration providing oxygen and removing carbon dioxide. It is also an excretory organ.
One of the most amazing things about the placenta is its role in stem cell physiology, which is only recently being studied. The placenta may prove to be a non-controversial source of hematapoetic stem cells (HSC) and mesenchymal stem cells (MSC) as well amniotic epitherial (AE) stem cells and endothelial progenitor cells.