Five things to know about football at the Olympics in Rio

• The men's football tournament runs from August 4-20 with the 16 nations split into four groups of four.

The top two teams from each group go into the knockout stages. There are only 12 teams in the women's tournament forming three groups of four which starts on August 3.

That allows the two best third-placed teams to progress to the last eight before quarter-finals and semi-finals will determine the gold medal matchup on August 19.

There is a third-placed playoff between the two semi-final losers for the bronze medal in both competitions.

• A gold in the men's football tournament in the final at the historic Maracana stadium is one of Brazil's most wanted as it hosts the games for the first time.

Having won five World Cups and being crowned champions of South America eight times, Olympic gold is the only major honour to escape the Selecao.

They have won the silver medal three times with even the likes of Ronaldinho, Ronaldo and previously Neymar missing out.

Barcelona star Neymar -- who sat out the Copa America in June to take part -- returns to spearhead a strong squad with Brazil heavy favourites to finally break their duck despite the presence of world champions Germany and eternal rivals Argentina.

• Neymar will be one of three players over the age of 23 each side is allowed the select. The restriction introduced for the 1992 Barcelona Olympics was a compromise reached between football's governing body FIFA and the International Olympic Committee (IOC) to allow professional players to play without rivalling FIFA's prize asset the World Cup.

Despite that Neymar is far from the only world class talent to have carried the hopes of his nation in the Olympics.

Lionel Messi won his only honour with Argentina at the Beijing games in 2008 and Cristiano Ronaldo represented Portugal in Athens in 2004.

However, the restrictions only apply to the men's tournament. The women's competition is contested between full international sides.

• Following on from the success of taking football round the country at the London games four years ago, many stadiums that hosted World Cup fixtures two years ago will be used for both men and women's tournaments.

As well as the Maracana -- which will host both finals -- and the Olympic stadium, games will be held in Sao Paulo, Brasilia, Salvador, Belo Horizonte and as far away as the Manaus, nearly 3,000 kilometres away from Rio in the Amazonian jungle.

• Although not considered the peak of the sport, men's football has been in every Olympics bar 1896 and 1932. The first appearance at the Olympics dates back to before the first World Cup and changing regulations throughout the decades has allowed for a far greater variety of winners.

A total of 18 countries have landed gold with Hungary and Great Britain leading the way with three wins each.

Football was introduced to the women's programme in 1996 and has since been dominated by world champions the United States, who have won four golds and a silver in the five games since.