(NBC News) - The countdown to the Rio 2016 Games formally began Thursday morning with the ceremonial lighting of the Olympic torch in southern Greece.

The torch will travel through Greece before reaching Brazil on May 3. Some 12,000 people will carry the flame on its journey to the Maracana Stadium for the Opening Ceremony on August 5.

Here are 16 things to know about the famous flame.

1. The Olympic flame is one of the best-known symbols of the Games. The flame in Olympia, Greece — where the ancient event took place — was lit using the rays of the sun. It is still lit using the sun in front of Olympia's ruins. But the International Olympic Committee has a backup plan in case of poor weather. A rehearsal is always held on a sunny day with another flame kept on hand in case it is needed.

2. The modern flame was reintroduced for the 1928 Games in Amsterdam. The torch relay was established before the 1936 Games in Berlin. That event was organized by the Nazi party and the torch run went through countries where Germany wanted to increase its influence.

3. The longest torch relay for a Summer Games was for Beijing in 2008. According to the International Olympic Committee, the relay included 21,800 torch bearers. The torch went on a worldwide tour visiting cities such as London, Paris, and San Francisco before traveling in China. The 2008 Olympic Flame even reached the summit of Mount Everest.

4. Following Thursday's lighting, the torch will travel throughout Greece before reaching Brazil. The Brazilian portion of the relay starts on May 3 with a celebration in Brasilia.

5. The Rio Olympic flame will visit 329 towns and cities, including all of Brazil's 26 state capitals. It's estimated the torch will be able to be seen by about 90 percent of the country's population.

6. Organizers hope the relay route shows off the best of Brazil's beauty, culture, and diversity. Along the route, the torch will visit the wildlife and wetlands region of the Pantanal, the stunning beach of Bahia, the Amazon, and the Iguacu Falls.

7. There will be about 12,000 torch bearers on the relay. Each person will carry the torch for about 200 meters (656 feet).

8. In an Olympic first, a migrant will be a torch bearer this year. A resident of the Eleonas camp, near Athens, will be invited to carry the torch when it passes through the area. The camp mostly houses migrants from Afghanistan and Iran.

9. The torch has a unique design featuring five ribbons of color. Each color represents aspects of nature in Brazil. At the top is gold for the sky and the sun. Gold also reflects the ultimate achievement at the Olympic Games — most famously represented by a gold medal. Next is green for the mountains around Rio. Then comes blue for Rio's famous seascapes. Last is dark blue to represent the ground and land of Rio and Brazil.

10. The colored segments of the torch feature a wave design. The design mimics the black-and-white tiled promenade of Copacabana.

11. With Brazilian flare, the moment the torch's flame is passed from one torch bearer to another is being called "The Kiss."

12. The flame is sustained using gas. It is supposed to continually burn, but the flame has accidentally or deliberately been extinguished many times during relays. In 2013, a Kremlin guard used a lighter to reignite a torch in Moscow ahead of the Sochi Games.

13. The official uniform for the Rio torch relay is a white shirt and shorts with yellow and green trim. Rio 2016 organizers say the white represents peace and unity, the yellow symbolizes the Olympic flame, and the green brings in the color of the Brazilian flag.

14. The torch relay even has an official song "A Vida do Viajante" — or "The Life of a Traveler."

15. The torch relay ends on August 5 when the final torch bearer will light the Olympic cauldron at the Rio 2016 Opening Ceremony at the Maracana Stadium.

16. The selection of the final torch bearer and is always shrouded in mystery. At the 1996 Summer Olympics in Atlanta, Muhammad Ali had the honor. During London 2012, the cauldron was lit by seven aspiring young athletes.