Thirty-four histological serial sections from the Radlanski Collection, Charité-Universitätsmedizin Berlin, Germany, ranging between 15 and 270 mm CRL (weeks 6–28) were used for this atlas (Figs. 3.1 and 3.2; Table 3.1). The use of this material was approved by the ethical committee of Charité-Universitätsmedizin Berlin, EA4/017/06. The specimens were obtained from legal or spontaneous abortions and autopsies, and no part of the material gave any indication for spontaneous malformation. Most of the funding for the laboratory processes described below was provided by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the framework of research projects Ra 428/1-1, 1-2, 1-3 1987–1993, Ra 428/1-9 2008–2011, and Ra 428/11-1 2012–2016.