Enabling young children to achieve their full developmental potential is a human right and an essential requisite for sustainable development. Given the critical importance of enabling children to make the best start in life, the health sector has an important role and responsibility to support nurturing care for childhood development. Many interventions for reproductive, maternal, newborn and child health (including for nutrition, mental health and HIV prevention and care) have a direct impact on child development. Moreover, the health sector has access to families and caregivers during the early childhood period. Until now, WHO has not had guidelines specifically on improving early childhood development (ECD). Existing WHO guidelines related to neonatal care; infant and young child nutrition; environmental health; prevention and treatment of childhood illnesses; violence and injury prevention; mental health; prevention of noncommunicable diseases; and support for children with developmental difficulties or disabilities, refer to the importance of respective interventions for ECD. However, they do not address ECD-specific interventions such as those related to responsive caregiving and early learning.