RecruitingProcedureSpermatogonial Stem Cell (SSC) Transplant and Testicular Tissue GraftingSpermatogonial stem cell transplantation through ultrasound guided rete testis injection and testicular tissue grafting will be performed for participants who have frozen testicular tissue prior to gonadotoxic therapy. The purpose of this study is to test the safety and feasibility of these transplant technologies and restore fertility for these participants.