The article discusses the emerging field of organ printing, which involves layer-by-layer additive robotic biofabrication of three-dimensional functional living tissues and organs using tissue spheroids as building blocks. Tissue spheroids are living materials with measurable, evolving, and potentially controllable composition and biological properties. The process of tissue fusion, inspired by developmental biology, allows for the self-assembly of these spheroids into functional tissues and organs. The authors highlight the advantages of organ printing, such as the ability to engineer large-scale industrial robotic biofabrication of living human organ constructs with built-in perfusable intraorgan branched vascular trees. They also address the limitations of traditional biodegradable solid scaffold-based approaches in tissue engineering, emphasizing the need for new technologies that can overcome challenges like vascularization and precise cell placement. The article concludes by discussing the potential of organ printing to transform tissue engineering and the importance of integrating developmental biology principles into tissue engineering practices.The article discusses the emerging field of organ printing, which involves layer-by-layer additive robotic biofabrication of three-dimensional functional living tissues and organs using tissue spheroids as building blocks. Tissue spheroids are living materials with measurable, evolving, and potentially controllable composition and biological properties. The process of tissue fusion, inspired by developmental biology, allows for the self-assembly of these spheroids into functional tissues and organs. The authors highlight the advantages of organ printing, such as the ability to engineer large-scale industrial robotic biofabrication of living human organ constructs with built-in perfusable intraorgan branched vascular trees. They also address the limitations of traditional biodegradable solid scaffold-based approaches in tissue engineering, emphasizing the need for new technologies that can overcome challenges like vascularization and precise cell placement. The article concludes by discussing the potential of organ printing to transform tissue engineering and the importance of integrating developmental biology principles into tissue engineering practices.