Our baby is the size of...

a LIME

From the internet..baby center
The most dramatic development this week: reflexes. Your baby's fingers will soon begin to open and close, his toes will curl, his eye muscles will clench, and his mouth will make sucking movements. In fact, if you prod your abdomen, your baby will squirm in response, although you won't be able to feel it. His intestines, which have grown so fast that they protrude into the umbilical cord, will start to move into his abdominal cavity about now, and his kidneys will begin excreting urine into his bladder.

Meanwhile, nerve cells are multiplying rapidly, and in your baby's brain, synapses are forming furiously. His face looks unquestionably human: His eyes have moved from the sides to the front of his head, and his ears are right where they should be. From crown to rump, your baby-to-be is just over 2 inches long (about the size of a lime) and weighs half an ounce.

From my book: What to expect when expecting!!
Your baby has more than doubled in size during the past three weeks, Weighing in now at 1/2 ounce and measuring (crown to rump) about 2 1/2 inches. About the size of a large fresh plum, your baby's body is hard at work in the development department. Though most of his or her systems are fully formed, there's still plenty of maturing to do. The digestive system is beginning to practice contraction movements (so your baby will be able to eat), the bone marrow is making white blood cells, and the pituitary gland at the base of the brain has started producing hormones.