Since China began to reform and open up four decades ago, it's seen two-speed growth -- economic miracles in the cities but large rural areas left behind. Millions of farmers moved to the cities seeking jobs, leaving their young children at home. The oldest of these "left-behind" children have now grown up. Our reporter Tao Yuan has been finding out how a childhood without their parents affected them.

By day, Pan Shuguang drives a truck to earn a living. But he says this is what defines him - a family man and father of a five-year-old child. His parents weren't around through much of his childhood. He wants to be a better father.

PAN SHUGUANG "I had a very lonely childhood. I don't want my boy to go through what I went through."

This is where Pan grew up with his grandparents. His parents worked thousands of miles away in factories or construction sites, and only came back to visit once a year. China's army of migrant workers may have been the unsung heroes of its economic miracle, but it took a toll on the children they left behind. Pan's grandmother says he had good grades in school, but he quit early and left for the city to find work.

HUANG CHUNYING PAN SHUGUANG'S GRANDMOTHER "His parents sent home money to put him through school, but he wanted to start making his own contribution to the family."

At a young age, he felt the responsibilities of an adult. In this village school where Pan studied, many children are still growing up without their mums and dads. Many of their parents had hoped to keep them close. But the high cost of living in cities is daunting. And China’s household registration system means these children can't attend city schools, or access other social benefits outside their hometowns. This boy says he misses his parents every day, and dreams about them at night. This girl simply cannot stand the topic.

TAO YUAN SICHUAN PROVINCE "China's growth has sprouted some of the world's most modern cities. But its villages have been left behind. The growing divide means China will continue to see the massive internal migration of the last few decades. For many of these children, separation has become a quietly accepted norm, alongside a heavy emotional burden."

There's no comprehensive study on what China's left-behind children have grown up to become. Many drop out of school early to start low-end jobs. A lucky few go off to college, and graduate to become real city people, like 25-year-old Wen Ding - now a graduate student at one of China's best universities. In the eyes of his fellow villagers, his future sparkles with promise. But he says deep down, he carries a scar.

WEN DING "Honestly, there ARE psychological problems. For example, I have a feeling of inferiority. And I like to anchor my emotions on an object."

Wen's parents are still working far away, and only stay in touch with their son through video chat. I asked his mother if she ever felt bad for leaving her son.

QI MIAO WEN DING'S MOTHER "Yes, we worried so much about him. He only had a great-grandmother to take care of him. But we also wanted to create a better future for him."

WEN DING "My parents introduced me to the outside world, and made me want to embrace it. Without the money they worked so hard to earn, it wouldn't have been possible for me to go to school."

A trade-off between economic necessity and a happy family. Pan will soon face pressure enrolling his son in a city school.

PAN SHUGUANG "I try not to worry too much about the future, just now. And now, I just want to spend more time with my son. I just want him to be happy."

TY, CGTN, Sichuan Province.