Fertilization occurs when a sperm successfully penetrates the egg. This can be achieved through conventional IVF, where multiple sperms are placed with an oocyte, or through intracytoplasmic sperm injection (ICSI), where a single sperm is injected directly into the egg. Histologically, this involves the interaction between the sperm and the oocyte's cellular structures, such as the zona pellucida and the cytoplasm.
