Human Embryology is the study of the development of a human embryo from fertilization to the end of the eighth week of pregnancy. This process begins when a sperm cell fertilizes an egg cell, forming a zygote. The zygote then undergoes multiple cell divisions, eventually forming a blastocyst that implants into the uterus. During the embryonic stage, the basic structures of the body begin to form, including the heart, brain, and limbs. By the end of the eighth week, the embryo has developed most of its major organs and systems, transitioning into the fetal stage of development.