Core Insights - Researchers have successfully induced stem cells to develop into a fluid-filled amniotic sac model, measuring approximately 2 centimeters in diameter, which corresponds to the size of an amniotic sac surrounding a 4-week embryo, providing a new avenue for studying early pregnancy [1][2] Group 1 - The amniotic sac is a transparent membrane that forms a fluid-filled pouch to protect the developing embryo, but obtaining and studying this tissue in early pregnancy has been challenging [1] - The study published in "Cell" showcases the most advanced amniotic sac model to date, highlighting its large scale and reproducibility as significant advantages [1] - The model was created by stimulating embryonic stem cells with a signaling molecule on the first and second days, followed by placing the cells in a culture medium, leading to the formation of miniature fluid-filled sacs over three months [1] Group 2 - The researchers observed that these cells mimicked the characteristics of a 4-week human amniotic sac, forming a double-layered membrane structure filled with fluid, similar to the yolk sac structure that provides nutrients to the embryo [2] - The volume of the amniotic sac is sufficient for the research team to extract and analyze the fluid, which is rich in proteins and metabolites crucial for fetal health, resembling substances found in human amniotic fluid during later stages of pregnancy [2] - There is uncertainty regarding the model's accuracy in simulating later-stage amniotic development, which is essential for studying severe complications arising from amniotic damage [2]