The Unit offers state-of-the-art technology for the manipulation of the mouse genome. It is a combined facility for both gene targeting in embryonic stem (ES) cells and mouse transgenesis. Other available techniques in our laboratory include the establishment of ES cell lines from mouse embryos and in vitro differentiation of ES cells. We are responsible for the cryopreservation of genetically modified mouse strains through both sperm and embryo freezing. Our Unit also manages the re-derivation of mouse lines and management of tool strains (Cre and Flp transgenic lines and reporters among others) in collaboration with the CNIO Animal Facility. It also provides support to CNIO Groups with projects involving mouse models, ES cells, induced pluripotent stem (iPS) cells, and embryos.