Infertility today represents a global problem. Male factor contributes in approximately 50% of infertile couples. In the last decade we are witnesses of the decreased quality of semen and the increased frequency of testicular cancer and cryptorchidism. Currently, the assessment of semen quality is based on the routine semen analysis including sperm count, morphology and motility. Although variation and combination among these three main factors articulate few diagnosis, nowadays developed assisted reproduction techniques (ART), especially intracytoplasmatic sperm injection (ICSI) may be used to treat most of the male infertility problems. In general we can say that traditional semen parameters provide a limited degree of diagnostic information, thus we are aware that these indexes of diagnosis should be revisited, which includes more specific test of sperm assessments, such as DNA tests and sperm proteome. Spermatogenesis is a process that includes physiological, morphological and biochemical changes. After a complex process from the round diploid spermatogonia to haploid spermatozoa, a mature sperm just has an ability to fertilize a mature oocyte. If any errors occur during spermatogenesis process, appropriate sperm will not be produced. Thus, in our ART practice, it is important to understand normal physiology of spermatogenesis and find the reason of abnormal situation.