Azoospermia, which manifests as the absence of sperm in the semen, is a prevalent form of male infertility, affecting 10-15% of infertile men. Assisted reproductive techniques (ARTs) represent an excellent therapeutic option for azoospermic men, allowing infertile couples to achieve pregnancy. Microsurgical TEsticular Sperm Extraction (micro-TESE) ... is a surgical technique that allows for the extraction of spermatozoa from any active spermatogenesis pockets in the testis, even in patients with severe testicular failure. The extracted spermatozoa can subsequently be used in ICSI or IVF procedures. Men with normal or quantitatively diminished spermatogenesis (obstructive azoospermia or hypospermatogenesis diagnosis), have better chances for the success of sperm extraction, whereas spermatogenic arrest (SA) or the total loss of germ cells, known as Sertoli cell only syndrome (SCO) means the retrieval of any sperm viable for fertilization is unlikely, lowering the clinical benefit of such procedures. Current clinical tests used for the differential diagnosis of azoospermia are insufficient without a histological examination of testicular tissue. Testicular biopsy, or alternatively an exploratory TESE, remains the golden standard in the diagnosis of idiopathic male infertility. Novel biomarkers that can accurately predict the outcome of sperm extraction, and that are measurable in semen or in blood plasma would represent an ideal, non-invasive alternative. Deep analysis of seminal plasma, the acellular fraction of semen, and of testicular interstitial fluid (TIF), the biological fluid surrounding seminiferous tubules with access to the bloodstream, can also offer new insights into the etiology of azoospermia and the cellular processes involved in testicular function.