INTRODUCTION: Today, psychological processes and brain is no longer looked at as something less scientific in comparison with physical processes, so mental diseases will become equal as physical diseases very soon. Until recently, brain functioning could be observed only in patients with cerebral lesions, after surgery, and on animals, but it is possible today to observe it directly with modern imaging techniques. AIM: The aim of this presentation is to point out that optimal health and functioning, which are basic assumptions of both neuroscience and psychotherapy is related to increased level of integrity and neural networks growth. METHODS: Therefore, neurological development can be seen as development determined by experience. More neural networks will be developed during critical periods then, ultimately, will be used. Environment in which child lives and develops determines which networks are going to live through, and those that were not stimulated are susceptible for neural extinction (pruning). Quality of parental relationship has basic impact on brain development. Mother's capacity to regulate newborn's affects is directly linked to future child's capacity to regulate his/her own affects. RESULTS: Positive experiences from an early childhood, together with positive genetic heritage, ensure proper brain development. First years in human life are also a period of most turbulent brain development, and those early experiences have disproportionally large impact on human brain development. CONCLUSIONS: Brain growth and differentiation are not only determined genetically but also with constant interactions with environment. This epigenetic brain information doesn't end in an early childhood. There is a lifelong redistribution of cortical networks, depending on individual experience, including creation of de-novo generation of neurons in adult hippocampus, as recently proved, and neuroplasticity is precondition for any persisted behavioral change, behavior, cognition and emotion.