Decaflon

As much as men hate to hear this, the human fetal blueprint is initially female. We all begin as a ball of cells that quickly differentiates into various body parts. At five weeks of gestation, the fetus sports a neural tube that eventually becomes the spine, but other than that, we all look like a wad of chewing gum. Then at six weeks' gestation, the outlines of eyes, arms, legs and a face (and let's not mention the tail that also shows up for a while) appear.