The contribution of Daniel Stern regarding the theoretical definition of early preverbal communication, later reformulated using the cognitive conceptualization of implicit knowledge (Schacter, 1994), is discussed in this article. This perspective describes early interactions between infant and caregivers communicating with eye contact, vocalizations, postures, and gestures, whose rhythm is assimilated by the infant. Stern, from the beginning, considered relevant the clinical implications that were further developed. In this article, I clarify the relevance of implicit knowledge during infancy considering the contribution of Daniel Stern and the one of the more recent research (Ammaniti and Gallese, 2014), extending subsequently the focus of implicit relational exchange inside the psychotherapeutic relationship and illustrating it with a clinical vignette.