The expression "nuclear complex" was first used by Sigmund Freud to designate what he would later call the "Oedipus complex." While still signifying from a genetic or structural point of view the universal Oedipus complex, the notion of the nuclear complex came to be used in the narrower perspective of psycho-pathology: this complex was described as the characteristic core of neuroses, and contrasted to pre-oedipal pathologies.