This book presents an overview of a new group of progenitor stem cells. Their origins were originally detected in light- and electron microscopical sections of plastic embedded human embryonal and fetal organs.The distribution of these cells can result in a large quantity of ectopic stem cells. The observation of these ectopic stem cells leads us to postulate the existence of a basic wave of stem cell progenitors. This process proceeds earlier and independently from germ cell migra...