All Olympic opening ceremonies tend to pay homage to the host country's past, and this one is no different.

An image of a Pau-Brasil tree — the wood that gave its name to the country — digitally appeared on the floor of Maracana Stadium a few minutes into the start of Friday night's opening ceremony for the Rio Games, as if in the Amazon rainforest.

It's the country's national tree, has been on the list of threatened Brazilian plants and it's illegal to cut the few trees that remain.

Brazil was thick forest when first inhabited more than 500 years ago, and organizers thought that was the logical place to begin the ceremony.

Even some of the most subtle things at the opening have a meaning. The curved shape of the stages used in the ceremony are a nod to Oscar Niemeyer, a key figure in Brazilian architecture.

The unofficial anthem of Rio de Janeiro is being featured prominently as the opening ceremony gets underway.

The song "Aquele Abraco" — which translates to "That Hug" — by Grammy winner Gilberto Gil played a role in both the closing ceremony of the London Games four years ago and in Brazil's bid for these Rio Games.

The song was the soundtrack for the opening video, which started precisely at 8 p.m. in Rio.

Gil is credited for helping revolutionize Brazilian music in the 1960s. He wrote Aquele Abraco not as a celebration piece, but as his farewell to Rio. He was jailed in 1968 after angering Brazil's military dictatorship and lived in exile in London from 1969 through 1972.

The first line of the song : "Rio de Janeiro is still beautiful."

From there, fireworks blasted from the top of the stadium and the Brazilian national anthem quickly followed. Among the most generally cited lyrics to the song are these: "Giant by thine own nature, thou art beautiful, thou art strong."

The official Brazilian flag has been hoisted by Rio de Janeiro's Environmental Police Command. Protecting and sustaining Brazil's environment will be a theme of the opening, and will continue throughout the games.

The opening ceremony did not mean a warm reception for everyone.

As Brazilian government officials took their seats, a smattering of boos could be heard in Maracana Stadium. It could be expected, given the political times in Brazil right now.

Many residents are upset over how much money was spent on these games, saying it could have been better-directed toward Brazilian needs. Interim President Michel Temer took over following the suspension in May of President Dilma Rousseff on impeachment charges.

And the booing didn't last long — when the show started, the crowd roared in delight.

Long lines are still outside Maracana Stadium, waiting to get through the copious team of security and into their seats for the opening ceremony.

But inside, the pre-show is underway.

Brazilian entertainer and television personality Regina Case is on the stadium floor, teaching fans in the stadium certain roles they will play in the show. Case says that 60,000 fans will be in the stadium, but she reminded the crowd that 3 billion will be watching on television worldwide.

Case told the crowd, "Here in Brazil, we like to party ... and we believe the people are made to shine." And she reminded the crowd that they are "the stars of this show" as the lights of the stadium dimmed and the only illumination was coming from the lights of thousands of fans' cell phones.

Outside, military vehicles, police and 35 checkpoints filled the streets near the stadium. Their presence created long lines and traffic jams.

Neither Brazil's Defense Ministry nor Rio de Janeiro police will say how many security personnel are on the ground to secure the Olympic opening ceremony. As many as 85,000 will be on site until the end of the games. That's twice as many as London four years ago. More would have been on the ground if Rio wasn't forced to cut about $550 million from the Olympic budget amid a recession.

Most of the nations marching in Friday's opening ceremony for the Rio Games will not have a head of state in Maracana Stadium to help cheer their arrival.

Officials had predicted as many as 100 heads of state would attend the first Olympics in South America. But that fell way flat, with about 25 expected to attend Friday night — in large part because of very uncertain political times in Brazil.

For now, the country essentially has two presidents. Interim President Michel Temer took over following the suspension in May of President Dilma Rousseff on impeachment charges.

Among those who are coming: US Secretary of State John Kerry.

Fans are filing into Maracana Stadium, as the opening ceremony for the Rio Games gets set to begin later Friday night.

Once considered the biggest stadium in the world with a capacity of nearly 200,000, Maracana Stadium now holds around 80,000 people.

Opened in 1950 for the World Cup, in which Uruguay beat the hosts 2-1 in the final, the stadium has been renovated many times over the years. Pele scored the 1,000th goal of his career there in 1969, and the field has been the site for countless major soccer matches at many levels.

Frank Sinatra, Tina Turner and Paul McCartney all played there in the 1980s to massive crowds of about 180,000. KISS, Sting, Madonna, Pearl Jam, the Rolling Stones and Prince are among the many other performers to grace Maracana's stage.

The stadium was the site of the 2014 World Cup final. Germany topped Argentina 1-0 for the title.

The closing ceremony is at the stadium as well, as are the opening and closing events of the Paralympics. (bbn)