Biology on Instagram: "Prenatal development. The process by which a human life forms and grows inside the womb, unfolding in three main stages. The germinal stage (weeks 1–2) begins with fertilization, as the zygote travels to the uterus and implants itself. During the embryonic stage (weeks 3–8), the major organs and body structures begin to form—such as the brain, heart, and spinal cord—while the heart starts beating and facial features emerge. Finally, the fetal stage (week 9 to birth) is mar

On this day in 1973, we met Sarah Jane Smith and the Sontarans for the first time #DoctorWho