Malnutrition in all its forms is closely linked, either directly or indirectly, to major causes of death and disability worldwide. The causes of malnutrition are directly related to inadequate dietary intake as well as disease, but indirectly to many factors, among others household food security, maternal and child care, health services and the environment. While most nutrition interventions are delivered through the health sector, non-health interventions can also be critical. Actions should target the different causes to reach sustainable change, which requires a multisectoral approach. This document provides a compact of WHO guidance on nutrition interventions targeting the first 1000 days of life. Focusing on this package of essential nutrition actions (ENA), policy-makers could reduce infant and child mortality, improve physical and mental growth and development, and improve productivity. Part I presents the interventions currently recommended by WHO, summarizes the rationale and the evidence, and describes the actions required to implement them. The document uses a life course approach, from pre-conception throughout the first 2 years of life. Part II provides an analysis of community-based interventions aimed at improving nutrition and indicates how effective interventions can be delivered in an integrated fashion. It shows how the ENAs described in the first part have been implemented in large-scale programmes in various settings, what the outcomes have been, and to examine the evidence for attribution of changes in nutritional outcomes to programme activities.