Our journey of life began as a single-celled zygote—
the product of the fusion of the genetic material from our father’s sperm cell and our mother’s ovum.
During the next 2 weeks—the germinal phase of prenatal development—that single cell became a mass of cells,
doubling again and again as it moved down the fallopian tube before implanting in the wall of the mother’s uterus.
During weeks 3 through 8—the embryonic phase—we began to draw our nutrients from our mother’ blood,
and the general-purpose cells differentiated into specialized cells, allowing our organ systems to begin forming.
By the time we reached the fetal phase at 9 weeks after conception, all of our organ systems were present, although they were not yet fully functional.
During the time remaining until birth (usually around 38 weeks after conception), the fetus grew dramatically
and each of the organ systems continues to mature, preparing the fetus for life outside the womb.