Spermatozoa production takes place in the testicular seminiferous tubules and the process is known as spermatogenesis.  At the end of this process, a germ cell generates 4 mature spermatozoa which will survive in the human body for between 62 and 75 days.  The final stage in spermatogenesis, known as spermiogenesis, is a cell differentiation and maturation process consisting of the change from spermatids to spermatozoa.  As can be seen in the picture, the spermatids develop from secondary spermatocites and have already undergone Meiosis I and II division. They have a normal set of chromosomes (haploid) which means that fertilisation of a mature egg can take place. Therefore, and despite the fact that they are immature cells, they can be used in assisted reproduction techniques using ICSI when there are no mature sperm in samples taken from the ejaculate or testicles. […]