Psychoses are one of the main groups of mental disorders. Based on the observation that initial treatment delay for psychoses often led to poor prognosis, an interest was born in identifying and defining early psychotic stages, currently termed the Clinical High Risk (CHR) concept. Representing early stages of psychosis with a risk of progressing to more advanced stages, different types of risk groups were defined. The CHR concept also allowed for the proposal and development of a staging concept as applied to psychotic disorders. The CHR concept, particularly through the staging system, has also enhanced our biological understanding of psychosis as biological processes altered in psychosis, such as striatal dopamine or cortical thinning, which can in many cases be shown to progress across stages. This may in turn allow for better identification of biological treatment opportunities, and also facilitate the development of reliable biomarkers for psychosis.