Final answer:
The developing human organism from the 8th week of gestation through delivery is known as a fetus, which represents the last stage of prenatal development before birth.
Step-by-step explanation:
From the 8th week of gestation through delivery, the developing cells are known as a fetus. This is the term used to describe the human organism from the end of the eighth week post-fertilization until birth.
During the fetal period, which lasts about 30 weeks, the structures and functions of the immature organ systems formed during the embryonic period are fully developed. The fetal stage is marked by significant growth and differentiation, ensuring that the newborn is capable of surviving outside of the womb upon delivery. The fetal stage is critical for the development of most organs and the sensory systems, preparing the fetus for life after birth.