Abstract: The organizer is a signaling center with inductive capacity during embryonic development. Since its discovery, it has been a central topic in developmental biology for studies on axis formation and cell fate determination. Over the past century, extensive studies have elucidated the organizer’s pivotal roles in morphogenesis and tissue induction, and have identified key molecular signals, including BMP, Wnt, Nodal and Huluwa, as core regulators of organizer activity. With the advancement of evolutionary developmental biology, organizers have been recognized as a developmental regulatory system functioning across diverse animal taxa; however, the evolution of its regulatory networks and lineage-specific differences of inductive mechanisms remain to be further elucidated. More recently, the rapid development of single-cell omics technologies, together with the emergence of stem cell–derived embryoid models, have provided new opportunities to dissect the cellular heterogeneity, regulatory networks, and evolutionary origins of organizer function. Here, we summarize the historical progress of organizer research, integrate insights from molecular mechanisms and evolutionary conservation, clarify that the organizer can act as a core evolutionary developmental module, and discuss the implications of organizer studies for artificial embryos and tissue engineering. We propose a perspective in which the organizer is best understood as an evolvable and reconfigurable developmental module rather than a strictly defined embryonic structure.

Key words: organizer, body axis formation, evolutionary developmental biology, new model animals, embryoid