South Sudan gained independence in July 2011 but after two decades of conflict with the north, relations with Sudan remain fraught. These maps show the extent of the divisions between a richer, Arabic-speaking, Muslim Sudan and a poorer South devastated by years of conflict and neglect.
Both Sudan and the South are reliant on oil revenue, which accounts for 98% of South Sudan's budget. They have fiercely disagreed over how to divide the oil wealth of the former united state - at one time production was shutdown for more than a year. Some 75% of the oil lies in the South but all the pipelines run north.
The two Sudans are very different geographically. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
In the Sudanese states of Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In South Sudan, boreholes and unprotected wells are the main drinking sources. More than 80% of South Sudanese have no toilet facilities.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. In Sudan, many of the residents of war-affected Darfur and the border states of Blue Nile and South Kordofan depend on food aid. The UN says about 2.8m people in South Sudan required food aid in 2013.
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