This chapter provides an overview of how Colwyn Trevarthen developed his interests from physiology to neurophysiology, from plants and animals to human infants and, on this journey, developed powerful arguments for just how brilliant babies are. One person to have had a decisive influence over Trevarthen's career was Archie McIntyre, professor of Physiology at the University of Otago, who suggested that he should apply to do a PhD with Roger Sperry. Trevarthen had journeyed from New Zealand to the United States and then to France, and from looking at ecology and plants and living creatures, to thinking about the role of movement and vision in infancy when he became involved in the world of babies and toddlers. By training Trevarthen was a scientist with a knowledge of neurophysiology, particularly of movement and vision. But he also knew about psychology and development, about culture and language.