Early childhood is a time of intense and rapid changes. The development of brain architecture in the early period of a child's life is most susceptible to the influence of relationships and experiences. Early experiences are embedded in our bodies, with lasting effects on learning, behavior, physical and mental health. Early age is, therefor, a critical period for emotional development and the development of basic social competences upon which the child builds relationships and his own emotional well-being throughout his entire life. Despite this scientifically proven fact, the emotional development of a child does not receive adequate recognition and care from society at the level of the educational system and education policy. The result of neglecting the importance of the period of early emotional development is children at an early age with psychological problems that grow as the child grows, and opportunities for early prevention and intervention are missed. Significant shortcomings in the quality of the environment during that period, both family and institutional, can undermine the child's development, threaten their personal economic and social mobility in the future, and consequently undermine the sustainability and, no less important, the productivity of the entire society. The aim of this paper is to present some of the best confirmed theories, as well as the results of some recent research in the field of mental health of children at an early age.