Guardianship is the process by which citizens function as effective informal crime prevention and control agents. The concept was first intro­duced in Cohen and Felson's (1979) routine activity approach and was originally defined as "any spatio-temporally specific supervision of people or property by other people which may prevent criminal violations from occurring" (Felson and Cohen 1980). In spite of the capable guardian's central role in determining criminal victimization, research focusing exclu­sively on guardianship and the mechanisms that facilitate and inhibit it is limited, particularly compared to that of offending and victimization. Recent research has begun to address this gap in the criminological literature to reveal that guardianship against crime is effective when cit­izens are available and is boosted when they engage in monitoring or supervision of their surroundings and intervene when necessary. Empirical evidence demonstrates that guardianship intensity in residential environ­ments is a place-based characteristic, as it is critically determined by the opportunities available for supervision generated by spatio­physical and sociodemographic contextual factors.