Individual; it is an entity that is constantly developing, affecting its environment, being affected by the environment and changing. This development and change process of the individual can bring along adaptation problems. In order to understand the possible incompatibilities experienced by the individual with himself, others and the society, and to carry out studies to increase harmony, it is necessary to know what harmony and incompatibility are, what types of adjustment problems exist, what factors affect adjustment problems, and what can be done to prevent and intervene in adjustment problems. For this reason, this book, which deals with all development periods of the individual from birth to death and possible adaptation problems that he may experience, is a resource for experts and students working in the field.