A human brain begins assembling itself before most pregnancies are even confirmed: by four weeks of gestation, neurons are forming at a rate of 250,000 per minute, each one migrating to a precise location and wiring into billions of others. This film follows the science of that construction project through infancy, when the brain is more open to being shaped by experience than at any later point in life. It looks closely at vision as a case study, tracing how an infant's eyes and visual cortex develop only as fast as the brain can handle new stimulation, and at the real medical problem this creates for babies born with cataracts, where doctors must clear the obstruction without disrupting the visual system's development window. Neurologist Carla Shatz appears to lay out how much remains unknown, noting that memory, aspiration, and love are all encoded somewhere in these circuits, though scientists still have only a rough grasp of how the wiring actually produces a mind.