1 Early Stage of Invagination of the Inner Cell Layer (image) University of Vienna Share Print E-Mail Caption Early stage of invagination of the inner cell layer, the endoderm. Cells at the margins show a strong deformation. Credit Copyright: Ulrich Technau Usage Restrictions The image may only be used with appropriate caption or credit. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.