This book project illustrates how members of the Association of Collegiate Alumnae (ACA), most prominent among them Milicent Shinn, a graduate of the University of California, engaged in the study of early childhood development. Their efforts culminated in an unprecedented network of at-home scientific observation of infants that spanned the North American continent. Shinn and her female peers were inspired by contemporary scholarly enthusiasm for the physiological and mental development of infants and toddlers. During the last decades of the nineteenth century, men of science discovered in their own and others’ offspring, to borrow Charles Darwin’s phrase, “objects of natural history.” On the basis of the unpublished papers of Milicent Shinn and the correspondence of other members of her network, this project reveals how the ACA’s collective at-home observation of babies transformed the nursery into a laboratory and mothers into scientific observers. The practices developed by Shinn and her network of college-educated mothers blurred distinctions between university and home, expert and amateur. The most visible outcome of the network’s enterprise was Shinn’s authoritative 1908 study The Development of the Senses in the First Three Years of Childhood. This work identified emotions, most notably pleasure and interest, as the driving forces in the evolution of the human mind.