Over 200 million children under the age of 5 years in low and middle-income countries do not reach their developmental potential, largely due to lack of adequate nutrients and lack of psychosocial stimulation. Stunting (length-for-age < -2 z-scores) is an indication of chronic undernutrition. Guatemala has the high rates of stunting in the Western Hemisphere (over 40%). This trial examines the effect of providing a micronutrient powder manufactured in Guatemala vs. placebo and an early learning environment vs. no early learning environment on the growth, health, and development of young children in Guatemala.

The plan is to implement a clustered randomized placebo controlled trial with an infant phase (6-12 months of age) and a preschool phase (36-48 months of age). For the infant phase, the investigators will use ProPAN (Process for the Promotion of Child Feeding) in the development of the evaluation and intervention, with modifications as necessary for the Guatemalan context. ProPAN is a tool developed and distributed by the Pan American Health Organization to develop, implement, and evaluate interventions and programs to improve infant and young child diet and feeding. ProPAN includes four modules:

Module 1: Assessment Module 2: Testing Recipes and Recommendations Module 3: Intervention Module 4: Monitoring and Evaluation

For the preschool phase, the investigators will use an evidence-based school readiness intervention (Little By Little) that has been shown to be effective with Hispanic preschoolers. The intervention will be implemented through the Association for the Prevention and Study of HIV/AIDS who will train and supervise the community health workers. By working directly with a local non-profit organization, the project will be well positioned to inform strategies to scale up the intervention on a community wide basis, if beneficial effects are shown.

The project examines the effects of an integrated intervention that includes both micronutrient powder added to food and responsive feeding for infants or school readiness for preschoolers. The primary aim is to examine how an integrated micronutrients + responsive feeding/school readiness intervention changes the development (primary outcome), growth and micronutrient status (secondary outcomes) of young children. The investigators will focus on infants (6-12 months) when the risk for micronutrient deficiencies is high, as they transition from breast feeding to complementary feeding and the family diet. The investigators will focus on preschoolers (36-48 months) to examine if micronutrients + a school readiness intervention can improve children's school readiness skills. The design includes neighborhood clusters randomized into four groups: 1) micronutrients plus responsive feeding/school readiness 2) micronutrients only, 3) placebo plus responsive feeding/school readiness, and 4) placebo only.

The investigators will test the following hypotheses:

1. Children in the two micronutrients groups have better change from baseline in development (primary outcome), growth and micronutrient status (secondary oitcomes), than children in the two placebo groups.
2. Mothers and children in the two responsive feeding/school readiness groups have better change from baseline measures of child development than those in the two control groups.
3. The impact of the responsive feeding/school readiness intervention is greater in the micronutrient groups than in the placebo groups. Children in the micronutrients plus responsive feeding/school readiness group have better change from baseline in development than children in any of the other three groups.

Inclusion Criteria:

• Child speaks Spanish.
• Child is age 6-12 months or age 36-48 months.
• Child must be undernourished (length and height for age < -1 z-score).
• Child does not have any obvious health or developmental problems that would interfere with growth, nutrition, or development.
• Child will remain in the area for the subsequent year.
• Parent or legal guardian of the child is age 18 years or older.
• Parent or legal guardian speaks and understands Spanish.
• Parent or legal guardian lives with child in study community.

Exclusion Criteria:

• Child is not age 6-12 months or 36-48 months.
• Child has severe stunting (length and height for age < -3 z-scores).
• Child has identified conditions that could interfere with their development and growth.
• Child is severely anemic (hemoglobin < 7).