A baby's brain is a mystery whose secrets scientists are just beginning to unravel. The mystery begins in the womb -- only four weeks into gestation the first brain cells, the neurons, are already forming at an astonishing rate: 250,000 every minute. Billions of neurons will forge links with billions of other neurons and eventually there will be trillions and trillions of connections between cells. Every cell is precisely in its place, every link between neurons carefully organized. Nothing is random, nothing arbitrary. One way a newborn is introduced to the world is through vision. The eyes and the visual cortex of an infant continue to develop after birth according to how much stimulation she can handle. What happens to the brain when a baby is born with a visual abnormality? Infant cataracts pose an interesting challenge to scientists: How to remove the visual obstruction without compromising brain development. In response to the demands of the world, the baby's brain sculpts itself. When we are babies, our brains are more open to the shaping hand of experience than at any time in our lives. In response to the demands of the world, the baby's brain sculpts itself. Scientists have begun to understand how that happens, but as Neurologist Carla Shatz says, "There's a great mystery left. Our memories and our hopes and our aspirations and who we love all of that is in there encoded in the circuits. But we only have the barest beginnings of an understanding about how the brain really works."