Many children in developing countries face hunger, disease and other humanitarian crises. Some are denied their childhoods when they are forced to work or when lengthy wars turn them into refugees or soldiers.
War and poverty take a heavy toll on the world's youngest, and many do not reach the age of five. Lack of access to health care puts babies at risk, and millions of children die from treatable illnesses like diarrhoea, pneumonia and measles that are no longer a serious problem in richer countries.
In tropical climates, many children suffer regular bouts of life-threatening malaria and live under the threat of other diseases that can kill, paralyse or blind, or simply take all their energy away.
The global AIDS pandemic has orphaned many children and left them in the care of grandparents or looking after themselves. Treatment for HIV-positive children has been slow in coming.
Hunger hits children hard, stunting their growth when it goes on too long, and threatening lives when crops fail, drought hits or prices skyrocket out of reach. Hunger and malnutrition contribute to a third of child deaths, the U.N. World Food Programme (WFP) says.
Many landmine casualties are children, and more than half of the world's refugees are children.
Armed groups often recruit children to fight, do hard labour, act as porters, or serve as sex slaves. Young refugees are vulnerable to other kinds of sexual abuse too, at risk of attack on the road or in refugee camps, or forced into prostitution or exploitation in exchange for basic necessities.
Several of the Millennium Development Goals set by world leaders in 2000 relate to children. The targets for the world to reach by 2015 include cutting the under-five mortality rate and infant mortality rate, and increasing the proportion of one-year-olds immunised against measles.
Children are regularly used by both aid agencies and media to highlight crises, raising a host of moral questions about photographs of children and ethical interview techniques.