The interaction between the amnion and the chorion towards the end of pregnancy, and their relation to the foetal compartment, are studied in this book. Recent findings using new morphological methods of investigation are brought together with previous findings from the fields of obstetrics and biochemistry to give a complete picture of the subject. Attention is turned mainly to the analysis of the cell and tissue structure which builds the boundary to the amniotic fluid. Light and electron microscopes are used to identify various cell functions. One particular area of interest is the microtexture of those structures responsible for the transport of substances and other mechanical processes. This overview of the latest information available from various fields aims to shed a different light on obstetric phenomena.