The Germ layers consist of about three layers of cells:
These three distinct layers are formed after a blastocyst’s inner cell mass undergoes a process of specific organization called gastrulation, which occurs after the blastocyst phase in embryonic development.
Published Clinical Citations
 ^ Jiao, Fei, Juan Wang, Zhao-Lun Dong, Min-Juan Wu, Ting-Bao Zhao, Dan-Dan Li, and Xin Wang. 2012. Human mesenchymal stem cells derived from limb bud can differentiate into all three embryonic germ layers lineages. Cellular reprogramming, no. 4 (July 9). doi:10.1089/cell.2012.0004. https://www.ncbi.nlm.nih.gov/pubmed/22775353
 ^ Solnica-Krezel, Lila, and Diane S Sepich. 2012. Gastrulation: making and shaping germ layers. Annual review of cell and developmental biology (July 9). doi:10.1146/annurev-cellbio-092910-154043. https://www.ncbi.nlm.nih.gov/pubmed/22804578
 ^ Zoldan, Janet, Emmanouil D Karagiannis, Christopher Y Lee, Daniel G Anderson, Robert Langer, and Shulamit Levenberg. 2011. The influence of scaffold elasticity on germ layer specification of human embryonic stem cells. Biomaterials, no. 36 (October 1). doi:10.1016/j.biomaterials.2011.09.012. https://www.ncbi.nlm.nih.gov/pubmed/21963156