Starting at implantation, your teeny tiny little one is already transforming your body (and soon, your life!). Read on to learn a few fascinating developments happening in your pregnancy this week.

1. Making Her/Himself at Home

The blastocyst has arrived at your uterus and is burrowing into the uterine wall. Some women experience mild cramping and spotting—also known as implantation bleeding—when this occurs. Another potential symptom: the presence of the pregnancy hormone progesterone could cause bloating.

2. The Great Divide

Once it’s implanted, the ball of cells divides into two: one which will become the embryo (your future baby), and the other becomes the placenta, an organ that will serve to deliver nutrients to and remove waste from your baby over the next 36 or so weeks.

3. Busy Body

Although it’s still microscopic, the embryo is rapidly developing and already boasts a neural tube, which is the beginning of the spine, backbone, and brain. If you know you’re pregnant, it’s important to start taking a daily prenatal vitamin. Look for one that contains at least 400 mg of folic acid, which is essential for preventing birth defects.