The NHLBI Transgenic Core’s main mission is to keep up with the latest advancements in genome engineering technologies and to provide state-of-the-art services to assist NIH scientists in generating genetically engineered animal models. In the past several years, the Core has successfully used the ZFN, TALEN, and CRISPR methods to generate gene-targeted mouse lines. The revolutionary CRISPR technology has enabled the Core to simultaneously target multiple genomic loci and achieve gene knockout in difficult mouse strains, such as immunocompromised mice. Besides developing these new technologies, the Core is continuing to provide a variety of services using the classical mouse genetic and reproductive methodologies, such as producing transgenic lines using the pronuclear microinjection method, generating knockout mice using ES cell-mediated homologous recombination and blastocyst microinjection, cryopreserving and resurrecting mouse lines. In addition, our core also offers services for injecting cells into immunocompromised mice for testing pluripotency through teratoma formation or studying tumor formation and tissue regeneration.