Since assisted reproductive techniques (ART) become more and more important with regard to family planning, it is a challenge for clinics to select the best sperm for the best oocyte. Therefore we are implementing and improving new techniques for gamete selection. But not only ART techniques as in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) have to be mastered perfectly, also the complete set of in vitro influences e.g. temperature, different ART media, etc. have to be monitored and controlled precisely. Especially ART media, in which fertilized zygotes are cultured until they reach the blastocyst stage play a crucial role. For the research on the influences of culture media we have established a mouse model system.