Final answer:
The period between conception and about week two of prenatal development is known as the germinal stage, which involves early cell divisions and concludes with blastocyst implantation in the uterus.
Step-by-step explanation:
In prenatal development, the time between conception and about week two is called the germinal stage. This is the earliest stage of human development, beginning at fertilization and involving the zygote's cell divisions and ending when the blastocyst implants into the uterus.
Post-implantation, the next phase is the embryonic stage, lasting from weeks 3 to 8, characterized by significant growth and development of the embryo. The fetal stage follows, starting at week 9 and continues until birth, with the development and maturation of the fetus's body and organ systems.