**Autologous Testicular Tissue Transplantation** is a procedure where a man's own frozen testicular tissue is transplanted back to help him father children. This is for men who had their testicular tissue frozen as boys before they went through cancer treatments that might damage their ability to have children. **Spermatogonial stem cells (SSCs)** are special cells in the testicles that can become sperm. Sometimes, boys with cancer have their testicular tissue frozen to save these cells. If, as adults, these men cannot produce sperm, this procedure might help by putting the preserved tissue back in the body. The goal is to restore the ability to make sperm naturally.

• The study is for men 18 and older who had their testicular tissue frozen as boys.
• Participants must be in a stable relationship and want to start a family.
• Doctors will check for risks before the procedure to ensure safety.