From the vaginal cavity those sperm cells move into the uterus and eventually make their way into the fallopian tube. And at this portion, at the thickest portion of the fallopian tube a single sperm cell will combine with this secondary OSI. And this is the process of fertilization. So fertilization takes place within this section. Now following fertilization we have an influx of calcium ions into the cytoplasm of that form zygote. And what the influx of calcium ions does is it initiates a set of metabolic processes.