Human embryonic development represents a crucial period of cellular specification and tissue organization, laying the foundation for all subsequent growth and differentiation. Because of its ethical and technical limitations, scientists use rare embryo samples and new in vitro models, such as stem cell-derived embryo-like structures. Our knowledge of human embryonic development has been completely transformed by single-cell RNA sequencing. This review covers the subjects of human embryogenesis, limitations in embryo research, the emergence of cultured embryo models, and how scRNA-seq has ultimately shaped the future of human developmental biology by becoming essential for analyzing developmental processes and evaluating the accuracy of stem cell-derived models.