Fibrin plays a critical role in hemostasis, thrombosis and wound healing by providing mechanical stability to blood clots that undergo deformation due to (patho)-physiologic conditions. Fibrinogen is rapidly depleted from the blood following traumatic injury which can lead to the development of coagulopathy, or bleeding; this has been correlated with an increased risk of death and a maladaptive inflammatory response. Importantly, trauma is the leading cause of death among young people. We have amassed considerable evidence that fibrinogen, fibrin, and clot structure are key drivers of thrombotic disorders. However, little is known regarding how changes in fibrinogen and fibrin clot formation during trauma coagulopathy may link hemostasis, inflammation, and immunity after trauma. In Specific Aim 1 I propose to take a multidisciplinary approach to systematically examine blood clot formation, structure, mechanics, and fibrinolytic properties in the trauma setting. In Specific Aim 2 I plan to examine the interplay between fibrin and the inflammatory cells, macrophages, in coagulopathy. Cutting edge experimental, imaging, and mechanical testing techniques will be used in vitro and in vivo assays with both reconstituted and patient samples to develop a holistic understanding of this complex process. In Specific Aim 3, the information gained during this examination will be used to inform the design of immuno-modulatory hemostatic biomaterials for potential use in trauma patients. Gaining the fundamental knowledge proposed here will inform the understanding of bleeding and hemostasis, the interplay between fibrin and inflammatory cells, and the use of fibrin in biomaterials.