In cases of azospermia (the absence of spermatozoa in the ejaculate), a testicular biopsy can tell us if there spermatogenesis (sperm production) and if the presence of spermatozoa can be found in the testes. Often if spermatozoa cannot be observed in a semen analysis, spermatozoa can be retrieved in several regions of the testes. The biopsy can be performed prior to IVF treatment as a diagnostic means, with the tissue frozen. Alternatively the day before or on the actual day of oocyte retrieval. If spermatozoa are recovered with TESE then the oocytes are fertilized by the method ICSI. Here, we see a single sperm being chosen from cells from the testes and being used fir ICSI.