The popularity reached by the genetic manipulation of laboratory animals to create new models for studying human diseases, produced in turn, that the techniques for assisted reproduction consolidate as routine in the laboratory of an animal facility. However, the costs of maintaining these mouse strains have increased deeply, and the physical space to housed these animals is practically the same one, for what we should admit that it is a concrete problem. In order to alleviate this problem is why embryo cryopreservation took importance in the early 90s. The cryopreservation technology has the advantage of being a tool to control the animal space at a low cost, but also has the benefits of being able to stop the risk of possible natural mutations, and genetic or infectious contamination (a tragic epidemic).Nowadays we can freeze embryos, sperm and ovaries to cover any situation of protecting the genetics of a mouse line. At the same time, the progress in the manipulation of the sperm and in the methods of in vitro fertilization does this task a more efficient process. With the sperm collected from a mouse there is enough material to fertilize approximately thousand of oocytes, which facilitates the task to preserve, to rederivate, and to expand or to distribute a mouse strain. Another application of this technology is to recover strains that otherwise it could be lost or by negligence, lack of breeding or by death. Today it is also possible to recover sperm from a death mouse and fertilize in-vitro up to 4 days after his dead.