What term is used to describe the tissue that forms during the early stages of embryo development?

The term "embryo" specifically refers to the developing organism in the early stages of pregnancy, from the moment of fertilization until the end of the eighth week. During this period, the embryo undergoes rapid cell division and differentiation, ultimately forming the various tissues and organs of the body.

In contrast, other options refer to structures that support embryonic development but do not encompass the entirety of the early developing organism. The chorion is a membrane that contributes to the formation of the placenta, while the placenta itself serves as the interface for nutrient and waste exchange between the mother and fetus. The amniotic sac, on the other hand, is the fluid-filled membrane that surrounds and protects the embryo. Each of these structures plays a vital role in supporting the embryo as it develops, but the term "embryo" most accurately describes the actual developing tissue at this stage.