This contribution, aided by clinical material, highlights the impact of early trauma on the structuring of the mental organization that patients bring to the therapeutic situation. Its focus is on how trauma organizes the mind/brain in childhood. Understanding the centrality of this process, often referred to as complex developmental trauma, relational trauma, or developmental trauma disorder, requires an appreciation of how early psychological development systematizes and organizes patients' patterns of relating to self and others. Changing how we think about the nature of complex developmental trauma enables both patients and therapists to better work through its enduring psychological imprint, a framework that creates significant challenges to growth and change.