The secondary oocyte (ovum) (I) is released from the ovary and gets fertilised if simultaneously sperm also reaches the fallopian tube and forms zygote (II).
The zygote further divides by mitosis and forms 2, 4, 8, 16 daughter cells called blastomeres. The embryo with 8-16 blastomeres is called morula (III). Morula further divides and transforms into blastocyst (IV) and then the blastocyst gets implanted in the uterus (V).