Many authors, particularly in the field of psychoanalysis, have demonstrated the intergenerational transmission of fundamental characteristics of personality structure. It has been found that unconscious modes of mental functioning, rather than contents, are transmitted. The structure of the unconscious has been stated to be transgenerational. Present-day research seeks to describe how not only contents but also functional modalities—that is, mental structures—can be transmitted in parent–child relationships and, in particular, in the caregiver-neonate relationship. Current studies describe these events in clinical terms. The author illustrates how his theory of the protomental, on which he has worked for many years and is still working, can not only describe but also explain in psychophysiological terms what is transmitted, and how it is transmitted, from the mother to the fetus and to the neonate.