Project Abstract The 19th century physiologist Rudolf Virchow presented the concept of the `Cell State', describing tissue as “a society of cells, a tiny well-ordered state, with all of the accessories — high officials and underlings, servants and masters, the great and the small”. Today, this analogy has proven apropos and much of our understanding of the interactions of cells within tissues is rooted in concepts from social networks, swarm theory, and collective behavior. However, despite our deep knowledge of the biological mechanisms underpinning cell-cell interactions, we know quite little about the interactions between tissues themselves and the social dynamics that play out at the boundaries where tissues meet. Such boundaries are crucial in processes spanning development, regeneration, tumor invasion, and wound healing, and a solid understanding not just of the underlying biology but how we might control it would greatly advance biomedical research. Our research targets this gap in knowledge from three directions: (1) developing new rules for studying what happens when tissues collide and heal; (2) using these rules to inform new tools to assemble tissues that take advantage of how tissues interact with each other; and (3) creating a new class of `cell-mimetic' biomaterials can integrate into tissues as if they are part of the tissue by mimicking key interactions that arise at tissue-tissue boundaries. The results of this research will inform not only our understanding of wound healing and tissue formation, but also improve our abilities to build new tissues for regenerative medicine and new biomedical implant materials.