The TGS is equipped with special microscopes connected to micromanipulators for the injection of DNA / RNA and ES cells into mouse embryos and provides instrumentation for freezing of mouse embryos. Additionally the TGS keeps selected mouse strains for the generation of mouse embryos and for the transplantation of modified embryos at the animal house. All mice are kept in specific-pathogen-free (SPF) livestocks in internally ventilated cages (IVCs) and are checked daily for their health.