&NA;There are major gaps in provision of services to vulnerable preschool populations that comprehensively link a child's strengths and challenges across health, home, developmental, social, and community systems. The purpose of this article is to describe the use of measures of functional assessment of essential activities in selfcare, mobility, communication, and social cognition in preschool children. Psychometric properties of the various tests are described. By developing a common language that simultaneously celebrates developmental accomplishments and addresses the ecology of enablement, early childhood professionals can prioritize comprehensive primary, secondary, and tertiary prevention strategies that optimize family supports and community participation.