Fertilization The process where two sex cells (gametes), such as the egg and sperm, come together to join their DNA and form an embryo. Related Articles: Endometrial scratch doesn’t increase success rates in a large randomized trialComplete guide to sperm qualityStudy compares IVF outcomes by follicle sizeGlossary: Pronucleus (PN)Complete Guide to Embryo Grading and Success Rates