Dispossessed: the South Sudanese without a nationality
"I'm living outside, I'm hungry, and I want to go to South Sudan," says Fatna Khamis Bilal.
She is one of an estimated half a million South Sudanese in Sudan who are running out of time.
A grace period for them to regularise their status in what was once their country comes to an end on 8 April.
Unless there is a last-minute intervention, almost all will no longer be legal residents of Sudan and many fear what could come next.
Ms Bilal took me to see her home-made shelter - little more than a brightly coloured sheet - on a patch of waste ground in Wad el Bashir in Omdurman, just across the River Nile from the capital, Khartoum.
More than 500 South Sudanese have assembled here, as they wait for transport to take them to their country.
Some are sleeping on the floor, and the walls of their new "houses" are bags and cardboard boxes containing all their possessions.
Many were born in Sudan, or have lived here for decades.
When South Sudan seceded in July 2011, Sudan decided all those it considered South Sudanese would lose their Sudanese nationality - giving them until 8 April to sort out their papers.
But South Sudan has not yet started issuing identity documents for its nationals in Sudan, and many South Sudanese say they have been turned away when they approached Sudanese officials about work permits.
Statements from officials have got many South Sudanese worried.'Four freedoms'
The governor of Sinnar state has reportedly said his state will expel South Sudanese on 9 April.
Just last month it seemed as though a solution had been found.
End Quote Carlo Musa South Sudanese chief
We've been out of our homes for three months... we need the help of the two governments to return to our country”
Sudanese and South Sudanese negotiators initialled a document, which was the first step in giving citizens of both countries the "four freedoms" in the other state - the freedom to go there and live there, the freedom to work, and to own property.
The four freedoms would allow South Sudanese - once they have proper documentation from the new state - to live and work in Sudan, and it would allow Sudanese groups like the Misseriya who live near the border to move freely into South Sudan with their cattle, as they have always done each year to seek water and pasture.
The next step was getting Sudan's President Omar al-Bashir and South Sudan's Salva Kiir to sign the agreement at a summit in Juba.
But Sudanese hardliners heavily criticised the deal - chief among them al-Tayyib Mustafa.
His Intibaha newspaper, which is extremely critical of South Sudan, has the biggest circulation in the country, and Mr Mustafa's influence is strengthened by the fact he is President Bashir's uncle.
He believes the four freedoms will allow South Sudan to infiltrate spies and military men into Sudan.
He thinks an influential group of South Sudanese politicians, named Garang's boys after former southern rebel leader John Garang, still want to bring down President Bashir.'Backlash'
Mr Mustafa maintains the four freedoms would be a disaster for his country.
"[The South Sudanese] should go, they should go to their country," he told the BBC.
"The government should differentiate between those who support the SPLM [South Sudan's governing party], and ordinary South Sudanese. I don't have any problem with them. But I think we should take care because they have their own plan to destroy Sudan, and to occupy Sudan."
This backlash, followed by days of fighting near the disputed border between Sudan and South Sudan's armies, lead to a postponement - or cancellation - of the Juba summit.
It now seems unlikely the four freedoms will be agreed on - in the short term at least.
In this climate many South Sudanese believe they have little choice but to leave.
Relatively well-off South Sudanese have been booking flights and travelling overland.
"I am going before April 8th," says John, "I have no choice."
The land route through Southern Kordofan has become very dangerous though - and 1,600 South Sudanese would-be returnees were held up by the recent fighting there.
Others have been trying to leave for months, without success.
Thousands are living rough - like Ms Bilal in Wad el Bashir - as they have given up their homes.'Risk of deportation'
Carlo Musa is a chief of the South Sudanese in Wad el Bashir. He's been in Sudan for 43 years, and worked as a tailor. No longer.
"Nobody is working here. We've been out of our homes for three months. We're going to South Sudan, but we need the help of the two governments to return to our country."
The good news is separation doesn't seem to have led to problems between the Sudanese and South Sudanese citizens, at least in Wad el Bashir.
"Between the two peoples I think there is no trouble, we are living, we go to market, there is nothing between the people," says Mr Musa.
But the South Sudanese he is responsible for are suffering.
"The people here are very tired. The men have no work, no food, that is our situation."
He and others say they don't have the money to travel to South Sudan, and in particular to transport all their worldly goods.
Others - like those who worked as civil servants or soldiers - are waiting around until they get their pensions, and in some cases, pay arrears.
Many fear that they may be forced to leave, once the grace period expires.
The UN's refugee agency, UNHCR, is concerned.
Following the expiry of the grace period, South Sudanese in Sudan will be considered as foreigners and so may "face a risk of deportation," says UNHCR's head of protection in Sudan Philippa Candler.
"At the moment we are optimistic there will not be large-scale deportations, but it is a risk for individuals because of their lack of legal status."
She says an extension of the transitional period would enable people to get the documents they need, and that the four freedoms would be very beneficial for South Sudanese.
But both of these seem unlikely to happen, and half a million South Sudanese find it impossible to predict their immediate future.
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. 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.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
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 said about 2.8m people in South Sudan would require food aid in 2013. The northern states tend to be wealthier, more urbanised and less reliant on agriculture.