The Cooperative Centers of Excellence in Hematology (CCEH) will be utilized by investigators for in vivo studies focused on molecular and cellular mechanisms involved in steady state hematopoiesis, the bone marrow niche, BM transplantation, and immune cell function. Centralization will prevent duplication of resources, ensure consistent supply of acclimated mice, and maintain high quality research infrastructure essential for conducting in vivo studies of hematopoietic stem and progenitor cell (HSPC) function. The Experimental Mouse Resources Core (EMRC) will provide CCEH investigators advanced resources for their studies using mice for murine and human transplantation models. The specific aims of the EMRC are: 1. Maintain on-site breeding colonies of essential mice to study human and murine hematopoiesis in vivo. For investigations focused on human hematopoiesis, colonies of NOD.Cg-PrkdcscidIl2rgtm1Wjl/J (NSG) and NOD.Cg-Ragtm1MomIl2rgtm1Wjl/SzJ and (NRG) immunodeficient mice will be maintained. In anticipation of future needs, a starter colony of the triple transgenic NSG-SGM3 (NSGS) mice that express human IL3, GM-CSF and SCF has been established and can be expanded as needed. Breeding colonies of C57/BL/6J, B6.SJL-Ptprca Pepcb/BoyJ (Boy/J), and the BoyJ x C57BL/6J (F1 cross) mouse strains will be maintained. The F1 cross is a unique strain and is not commercially available. Congenic mouse strains allow for simultaneous tracking of donor, competitor, and recipient cells. 2. Provide specialized core services and consultation to CCEH investigators. EMRC personnel will conduct irradiations, transplantations, serial sampling of peripheral blood, and compound dosing. The Core will harvest and provide tissues from transplanted mice to investigators for detailed analysis by the CCEH Flow and Tissue Cytometry Core. The ERMC will work closely with the Hypoxia Core to coordinate transplant of mouse and human HSPC collected and processed under hypoxia versus ambient air (Mantel et al., Cell 2015). The EMRC Director will coordinate with Core personnel all procedures, experimental design, methodology, and data interpretation. Expertise and infrastructure is in place to facilitate all aspects of BMT studies seamlessly for on-site CCEH members as well as PIs on a national level. 3. Serve as an educational resource for CCEH laboratories. Exceptional connectivity between the EMRC and the other biomedical cores as well as the Enrichment core will augment the research and training activities of the CCEH membership and their trainees. Training in the execution of high-quality in vivo studies will be a critical and essential component in training our next generation of scientists to be successful in research careers dedicated to the study of nonmalignant hematology. 4. Work in concert with other CCEH centers and investigators Nationwide to provide EMRC services to the community of scientists involved in nonmalignant hematology research.