Introduction -- Traditional One-Person Psychology -- Two-Person Relational Psychology for the Child and Adolescent Psychotherapist -- Key Pioneers in Two-Person Relational Psychology -- Key Concepts in Two-Person Relational Psychology -- Deconstruction of Traditional One-Person Psychology Concepts -- The  Neurodevelopmental and Neurofunctional basis of Intersubjectivity -- Putting it together: The 4 Pillars of the Contemporary Diagnostic Interview -- Setting the Frame in Two-Person Relational Psychotherapy -- Two-Person Relational Psychotherapy - Infants and Preschool Age Children -- Two-Person Relational Psychotherapy Elementary School Age Youth -- Two-Person Relational Psychotherapy Middle School Age Youth -- Two-Person Relational Psychotherapy -- High School Age Adolescents -- Supervision in Two-Person Relational Psychotherapy -- Appendix A: Developmental Milestones.-Appendix B: Contemporary Diagnostic Interview Case Formulation Tool.