Lost, Saroo Brierley ended up begging on the streets of India after being separated from his family.
But he was picked up by a charity that arranged for him to be adopted in Tasmania, Australia.
His story is now set to be featured in a new film, Lion, starring Nicole Kidman, charting his amazing life story.
Despite growing up in a loving family in Australia, he admits he spent years looking at maps and eventually at Google Earth for signs of the landmarks that he knew as a child.
And after recognising the village he was born in, Saroo traveled home - where he enjoyed an emotional reunion with his mother.
Saroo, who grew up in rural India, said that as a child he rarely had enough to eat and would often travel on trains in the area together with his brother.
But during one ill-fated trip in 1987, aged six, he had been dozing at a station with his brother and when he woke up he found that he was alone.
He said: "I opened my eyes and couldn't see my brother, but I saw a train in front of me with the door open and for some reason I thought he was on board.
"I think you could say that split-second decision changed my life forever."
Saroo made the 1,000-mile journey across the country and ending up in the north-eastern city of Kolkata, where alone and unable to speak the language, he became a beggar.
Luckily, he was rescued from the streets and put into an orphanage where he was adopted by an Australian couple – and ended up moving to Tasmania where he started a new life.
But the youngster, who dreamed of one day being reunited with his mother, said: "I remembered landmarks, for example there was a waterfall where we used to play and the dam.
"But I didn't know the city or town's name and finding a small neighbourhood in a vast country proved to be nearly impossible."
He did not give up though, looking at satellite images on Google Earth, zooming in and out of the map, exploring the web of railway lines criss-crossing India.
He said: "I thought to myself, 'Well, the first thing you're gonna see before you come to your hometown is the river where you used to play with your brothers, and the waterfall, and the architecture of this particular place where you used to visit quite a lot.' It has to be exactly the same, otherwise, if it's not, I'd just fly over and go somewhere else."
And then came the day he found the right place.
He said: "Everything just started to match. So I traced a road back that I would follow back as a child, and before I knew it I was looking at the suburb where I had grown up, and just on the right of it was the house I had grown up in. I couldn't sleep for that whole night."
He said: "I just thought the worst, I thought perhaps everyone's gone, my whole family's died, they've passed away.
"But lucky for me this lady came out of a doorway holding a baby, and she said, "Can I help you?" and I said to her, my name is Saroo and these are my family members' names.
"Within 10 minutes they came back around and they said, 'Now I'm going to take you to your mother'.
"And I couldn't believe it, because when I went around the corner, which was only 10, 15 metres around the corner, there were three ladies standing in front of an entrance to a house.
"And I looked at the second one and I thought, "There's something about you" — and it took me a few seconds but I decrypted what she used to looked like.
"She looked so much shorter than I remembered when I was a four-year-old child.
"But she walked forward, and I walked forward, and my emotions and tears and the chemical in my brain, you know, it was like a nuclear fusion.
"I just didn't know, really, what to say, because I never thought this point in time or ever seeing my mother would ever come true. And there I am, standing in front of her."