Histone code is essential tool in mammalian gametogenesis. The regulation of its establishment is responsible for the successful maturation of oocytes and spermatozoa, fertilization and embryonic development. There is the hypothesis that adequate changes of histone code are associated with the capability of fertilization and early embryonic development. This presumption will be elucidated based on mouse model usage, in vivo treatment with epigenetic modulators, followed by immunocytochemical analysis of gametes and embryos. The understanding of the regulation will provide possibilities for the improvement of embryonic development, including the knowledge transfer to human assisted reproduction.