Recent progress in cell micromanipulation has made it possible to achieve fertilization even with highly deficient male gametes, by injecting them directly to oocyte cytoplasm. This technique, known as intracytoplasmic sperm injection (ICSI), has proved efficient in most types of sperm pathology. However, ICSI fails when injected spermatozoa are not capable of supporting the process of oocyte activation or when they carry genetic abnormalities incompatible with normal embryonic development. Abnormalities of oocyte activation and the transmission of genetic anomalies to the progeny are also two major concerns relating to the clinical use of ICSI. The use of micromanipulation-assisted fertilization in cases of male germ cell maturation arrest, namely fertilization by round spermatid injection (ROSI), has brought preliminary clinical results, and the improvement of ROSI clinical efficacy remains a major challenge for future research.