Dissecting Human Embryogenesis With Blastoids: Insights Into Lineage Specification and Early Development

ABSTRACT Background Understanding human embryogenesis is a fundamental goal in developmental biology and reproductive medicine, but direct investigation of human embryos is limited by ethical and technical constraints. Stem cell–based blastocyst models have emerged as alternative systems to recapitulate key features of early human development in vitro. Methods We reviewed the literature on human stem cell–based embryo models, with a focus on blastoids. Relevant studies and review articles were identified through PubMed, covering blastoid generation strategies, model diversity, and insights into early lineage specification derived from blastoids and pluripotent stem cell studies. Main Findings Blastoids provide a versatile platform to model key aspects of human blastocyst development, including lineage specification, embryonic–extraembryonic interactions, and early morphogenesis. Recent studies demonstrate their utility in modeling implantation‐related processes, embryo–maternal interactions, and responses to genetic, environmental, and pharmacological perturbations. However, current systems remain limited by incomplete lineage representation and restricted capacity to model post‐implantation‐like development. Ongoing advances in stem cell biology and culture systems are expected to improve their fidelity and developmental potential. Conclusion Blastoids represent a promising approach for studying early human embryogenesis and are expected to expand their applications in reproductive biology and medicine.