Recently, research on the freezing of unfertilized eggs and ovaries aimed at preservation of fertility hasbeen advanced as a way to avoid iatrogenic infertility in young girls, whereas research in young boys is less emphasized due to the development of techniques the freeze sperm. A treatment for the preservation of fertility, however, has not been developed because sperm cannot be collected from prepubertal boys due to the immaturity of spermatogenesis. We developed an experimental model of vascularized testis transplantation with the aim of preserving fertility in prepubertal boys with childhood cancer and successfully achieved vascular anastomosis of a rat testicular artery and vein. We also found that when mouse testicular tissue was frozen under a magnetic field, tissue destruction is reduced as compared to the existing method of freezing. Combined application of super-microsurgery and a novel technique for freezing testis opened the way to long-term preservation of the testis and transplant studies.