Your baby is inside an amniotic sac. Within that lies the yolk sac, whose primary function is to provide nourishment while the placenta is developing. The yolk sac will disappear around the end of your first trimester. Meanwhile, the placenta is undergoing some structures that will attach it to your womb.
As for your baby’s growth, they are currently about 1.6 cm long, or 0.63 inches. In fact, the little one is growing very fast, approximately three to four-quarters of an inch. By next week, they will have doubled in size – cool, right?