The Chinese authorities are about to begin the country's first national census in 10 years.
More than six million workers have been hired for the huge task in the world's most populous country.
The authorities hope the census will clarify the number of migrant workers, which by some estimates is said to be more than 200 million.
Earlier this year, in a keynote speech, Premier Wen Jiabao said migrant workers needed better treatment.
The census is a mammoth undertaking - to account for every individual in a country with a population of more than 1.3 billion.
But that is the task facing the millions of census workers as they fan out across China.
The biggest challenge will be documenting migrant workers, who often have no fixed address.
In recent years tens of millions of Chinese have moved from the countryside to the cities in search of work.
But many of these workers have been marginalised and denied services.
It is also hoped that the census will reveal how many children there are in China, which is generally under-reported.
Because of the country's population controls, and the one-child policy, people often do not register extra children.
But the authorities now say that the penalties will be smaller if families come clean during the census.
And for the poorest families, they will be allowed to pay any fines through instalments.