During which range of weeks is a developing human called an embryo?

• A. 1-2
• B. 3-8
• C. 9-12
• D. 13-16

Answer: (B)

The stage when the basic body plan and organs first form is the embryonic period, which runs from conception through the end of week 8. During this time, organogenesis occurs, laying down the foundations for all major systems. Because of this critical development, the developing human is called an embryo specifically in weeks 3 through 8. The first two weeks are a pre-embryonic phase focused on fertilization and implantation, not yet the embryo stage. From week nine onward, development is described as fetal, with growth and refinement of structures rather than initial formation. Hence, weeks 3–8 are the embryo period.