Purpose: This clinical trial aims to explore the potential for human sperm production in vitro by sustaining a laboratory-cultured adult testicular environment. It also seeks to identify genetic factors contributing to human sterility and failed spermatogenesis. The study's primary objectives include: 1. Identifying genomic markers associated with sterility and failed spermatogenesis. 2. Developing an ex vivo (outside the body) testis organ-on-a-chip (iTestis) to support stem cell cultivation. 3. Determining whether human spermatogenesis can be re-created in vitro using stem cells nurtured in the iTestis model. Study Description: Researchers will analyze the genomic profiles of fertile and sterile male participants to map genetic abnormalities associated with sterility. Using testicular and skin tissue samples from participants, spermatogonial stem cells and pluripotent stem cells will be isolated and utilized to construct the ex vivo iTestis. This system will integrate genomic insights and prior research to foster human spermatogenesis outside the body. Participant Involvement: Participants will provide the following samples: * Blood sample for serum analysis. * A skin tissue biopsy. * Testicular tissue, obtained through fine needle aspiration (FNA) or testicular sperm extraction (TESE), as part of a routine procedure. All procedures will be conducted by the principal investigator and qualified research staff, ensuring participant safety and adherence to ethical guidelines.