TESE, or testicular biopsy, is a simple non invasive technique that requires only local anesthesia. This technique is used for patients with low or zero sperm counts in the ejaculate due to abnormalities in spermatogenesis or obstructive pathologies of the deferential ducts. Small fragments of tissue (biopsy)are removed from one or both testes to be analyzed in real time by an embryologist. Any spermatozoa recovered are used to fertilize the oocytes using ICSI. It is common practice to carry out TESE, before the female partner is prepared for hormonal stimulation and to freeze the fragments for use on the day of oocyte retrieval.