We examine the channels through which a randomized early childhood intervention in Colombia led to signi cant gains in cognitive and socio-emotional skills among a sample of disadvantaged children aged 12 to 24 months at baseline. We estimate the determinants of material and time investments in these children and evaluate the impact of the treatment on such investments. We then estimate the production functions for cognitive and socio-emotional skills. The effects of the program can be explained by increases in parental investments, which have strong e ffects on outcomes and are complementary to both maternal skills and child's baseline skills.