Prenatal development involves a series of intricate processes that lay the foundation for a child’s physical, cognitive, and social capabilities. Scientists categorize these stages into three main periods: germinal, embryonic, and fetal. Each period has distinct milestones and vulnerabilities to environmental influences. For instance, exposure to teratogens can significantly alter development during these stages. Understanding these phases is essential for anticipating potential developmental issues.

Which of the following accurately describes a characteristic or event associated with the embryonic stage of prenatal development?