The Karolinska Center for Transgene Technologies (KCTT), founded by Prof. Urban Lendahl and under the direction of Dr. Johannes Wilbertz, is a core facility for generation and banking of genetically modified mice. KCTT performs quality assured core facility functions in the above areas, and is linked to the cryobank unit and portal for export and import of mice to and from the Karolinska Institute. The cryobank unit is the Scandinavian node for the EMMA consortium. The mouse mutant bank today contains embryos from over 300 stocks. Karolinska Institute has also the capacity to re-derive mutants under germ-free conditions.