MC is key for a healthy/active lifestyle, but hardly documented in 1- to 3-year-olds. Besides determining actual MC-levels in Flemish toddlers for developing up-to-date reference values, the variability of MC-trajectories will be linked to cognitive and socio-emotional functioning with identification of individual and environmental determinants. Parents’/(day)caregivers’ knowledge, perception and needs regarding the daily promotion of MC will also be investigated.