"The nation’s children are everybody’s future, and what happens in those first three years, before school, really, really matters to that future," says child development expert Penelope Leach. In this program, ABC News anchor Diane Sawyer reports on the neurological connections that form in a child’s brain during pregnancy and early childhood and the long-term effects of sensory stimulation and deprivation during those formative periods. Commentary by Dr. Leach; UCLA’s Dr. Michael Phelps, co-inventor of the PET scan; and others sheds light on topics ranging from the complexities of language acquisition to a possible link between premature birth and ADD. (17 minutes)