(CNN) -- Veronica Campbell-Brown knows a thing or two about upsetting the odds.
The 29-year-old Jamaican sprinter has had to overcome grinding poverty to become one of the greatest Olympians her country has ever produced.
After being spotted running barefoot at a school sports day, Campbell-Brown burst on to the track and field scene when she won silver as part of Jamaica's 4x100 meters sprint team at the 2000 Sydney Olympics.
That was just the start.
She went on to win gold in the 200 meters at both the 2004 Athens and 2008 Beijing Olympics. Now she faces her toughest test at her fourth Games.
If she emerges triumphant at London's Olympic Stadium in August, she will be the first person in history to win three consecutive gold medals in the distance. She is in good form too. Last year she ran the 100 meters in 10.76 seconds, the second quickest time in history.
CNN's Human to Hero caught up with the Trelawny-born sprinter -- who hails from the same Jamaican parish that has given the world champion men's sprinter Usain Bolt -- to talk about London 2012, her rivals and why a third gold would be the icing on the cake.
Growing up in poverty
"I have five brothers, four sisters, so you can just imagine the competition in the house. It helped me be very competitive, strong and independent," Campbell-Brown said.
"I used to race the boys and win. So I knew I had a special gift and should work on improving it.
"When I was very young in primary school, we had a lot of sports days. I won the double there running barefoot. My coach and teacher said, 'You're very talented.' He recommended a high school, the 'Sprint Factory' (Camperdown High School). From that moment I came to the realization he was telling the truth."
Are yams the secret of Trelawny's success?
Campbell-Brown's birthplace has produced many top runners, including triple Olympic champion Bolt, U.S. athlete Sanya Richards-Ross and disgraced Canadian sprinter Ben Johnson.
"There's a lot of sprinters that come from Trelawny, it's so different, the country air. When I was growing up I didn't have central heating. I'd have to go and collect water from the river. I used to do a lot of walking," Campbell-Brown said.
"I think it's just hard work and determination. Jamaica is full of so many talents. My parents were farmers and used to plant their own yams that are starchy high in carbs. We took it right from the ground."
Life after winning gold in Athens
"I felt blessed. I don't think anything I've achieved has changed me. I am the same person. My personality doesn't change. You have to believe it to achieve it ... I visualized it and made it happen."
On giving back
Campbell-Brown has a charitable foundation aimed at empowering Jamaican girls through sport.
"I believe in giving back. When I was younger so many people helped me to become the woman I am today. So I feel, because I am in the position to help someone, I need to do it," she said.
"If I can touch just one life I will help someone, to try and help females in Jamaica to get a high school education, mentor them and make sure they keep a level head and point them in the right direction."
History beckons at London 2012?
As well as seeking a record third consecutive 200m gold, Campbell-Brown is also trying to qualify for the 100m, in which she was world champion in 2007 and runner-up in 2005 and 2011.
"There are a lot of great, talented women out there, hungry to perform at their best for the Olympics. There can only be one winner. It will be quite interesting. Everyone will have a great time watching it," she said.
"The Olympics are the highlight, the most recognized event in track and field. Everybody waits for the Olympics. It's very important to me. I'll be going for a fourth time.
"I've never won the 100 meters at the Olympics. If I win the 200 meters for a third time I will be the first woman to achieve that in history."
"It feels good. When I was a little girl my dream was always to get an individual gold medal. I have two, which is more than I asked for. A third will be the icing on the cake."