Baby's brain -- both hemispheres! -- is growing fast, generating about 100 new cells every minute. Arms and legs are emerging as joints start to form, and a permanent set of kidneys (baby's third!) is now in place.
Baby's about five to thirteen millimeters long (less than half an inch), and weighs less than a gram. The human blueprints are already visible. Baby still has a tail but is also beginning to form a digestive tract, lungs, nostrils, hands and feet, and a bump of a mouth. The liver, tongue, and lenses of baby's eyes are forming. There are beds for baby's fingernails, and the buds of teeth are forming in the gums. The baby's nerve channels and muscles are connecting, and the body can wiggle when the cells communicate. In just two days, from days thirty-one to thirty-three, the brain becomes one-quarter larger. If you were to have an ultrasound, it would be able to detect the beating heart, which shows up looking like a tiny flashing light.