Aids is one of the big problems facing children in Africa. It's the biggest single killer on the continent.
Around 23 million Africans have Aids.
In Ethiopia alone, 250,000 children under five have Aids.
The United Nations thinks Aids will eventually kill about a third of all young people living in Africa.
In Botswana and South Africa, up to a half of today's 15-year-olds will die of Aids.
But it's not just about children who actually have Aids.
Around 12 million children in Africa are 'Aids orphans' - so called because their parents have died from Aids-related illnesses.
In Swaziland, one in 10 families are headed by children because their parents have died of Aids-related diseases.