The starting point is the idea of discrimination, the common thread running through the essays collected, as the end result of interconnected processes: prejudices (emotional component), stereotypes (cognitive) and discriminatory acts (behavioral). Stereotypes and prejudices that guide perceptions and behaviors toward groups different from one's own are then examined through cognitive simplifications that are resistant to change and facilitate social exclusion. All this produces discrimination, understood as unjustified exclusion based on personal or social characteristics. The principle of non-discrimination, a cornerstone of international human rights law, protects the dignity and identity of every person, imposing on States not only negative obligations but also of prevention and repression of discrimination.