i think this too. even from conception to week 4 or 5 they grow so much! its hard to think that in the past week i have grown something from the size of a pinprick to something that i would be able to see in my hand... and yet there is still enough room in there, with my intestine, bladder, kidneys etc for it to have enough room (even at the size it is now) for me too not look any bigger!
extra-ordinary!