Infancy is an ideal time to study brain rhythms during sleep in humans. During the first year of life, infants' brains are rapidly changing. We’ve been perfecting our methods for two years and now need two additional E4 autonomic sensors to run a study with 15 infants, at three ages, characterizing the changes in two sleep brain rhythms: slow waves and sleep spindles, along with changes in autonomic sleep patterns, and cognitive, motor, and social-emotional development.