The placenta, an ancient organ, has evolved to play a critical role in supporting fetal development through nutrient and gas exchange, hormone secretion, and immune modulation. Despite its importance, the placenta remains one of the least studied organs. It is involved in embryo implantation, which is regulated by the trophoectoderm, and facilitates decidualization, a process essential for maintaining pregnancy. The placenta also acts as a barrier to protect the fetus from harmful substances, pathogens, and parasites. It interacts with maternal immune cells and the endometrium to adapt the immune system to the allogeneic fetus. The placenta expresses numerous proteins, some of which are specific to it and can serve as biomarkers for gestational diseases. The placenta shares many features with cancer, including metabolism, cell behavior, proteins, signaling pathways, and tissue microenvironment. This has led to the concept of "cancer as ectopic trophoblastic cells." Research in this area has identified several cancer biomarkers. The placenta also plays a role in immune regulation, helping to prevent maternal rejection of the fetus. It modulates the immune system through the expression of HLA-G, which induces a tolerogenic phenotype in immune cells. The placenta's role in decidualization and implantation is crucial for successful pregnancy. The placenta and decidua have a bidirectional relationship, with each influencing the other. The placenta also contributes to the development of the uterine immune system, which is essential for maintaining a pregnancy-friendly environment. The placenta's ability to regulate immune responses is vital for preventing miscarriage and ensuring a successful pregnancy. The placenta's role in immune regulation is complex and involves multiple interactions with maternal immune cells and the endometrium. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancy. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancy. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancyThe placenta, an ancient organ, has evolved to play a critical role in supporting fetal development through nutrient and gas exchange, hormone secretion, and immune modulation. Despite its importance, the placenta remains one of the least studied organs. It is involved in embryo implantation, which is regulated by the trophoectoderm, and facilitates decidualization, a process essential for maintaining pregnancy. The placenta also acts as a barrier to protect the fetus from harmful substances, pathogens, and parasites. It interacts with maternal immune cells and the endometrium to adapt the immune system to the allogeneic fetus. The placenta expresses numerous proteins, some of which are specific to it and can serve as biomarkers for gestational diseases. The placenta shares many features with cancer, including metabolism, cell behavior, proteins, signaling pathways, and tissue microenvironment. This has led to the concept of "cancer as ectopic trophoblastic cells." Research in this area has identified several cancer biomarkers. The placenta also plays a role in immune regulation, helping to prevent maternal rejection of the fetus. It modulates the immune system through the expression of HLA-G, which induces a tolerogenic phenotype in immune cells. The placenta's role in decidualization and implantation is crucial for successful pregnancy. The placenta and decidua have a bidirectional relationship, with each influencing the other. The placenta also contributes to the development of the uterine immune system, which is essential for maintaining a pregnancy-friendly environment. The placenta's ability to regulate immune responses is vital for preventing miscarriage and ensuring a successful pregnancy. The placenta's role in immune regulation is complex and involves multiple interactions with maternal immune cells and the endometrium. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancy. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancy. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to modulate the immune system is crucial for maintaining a pregnancy-friendly environment. The placenta's role in immune regulation is also important for preventing cancer, as it shares many features with cancer. The placenta's ability to regulate immune responses is a key factor in its role in maintaining a successful pregnancy