The 2016 Olympic Games officially start in Rio on Friday with the opening ceremony at the Maracana Stadium. 
Athletes from 206 nations and a refugee team are in Brazil to compete in 28 sports and be watched by a global audience of billions. 
The build-up has been dominated by a Russian doping scandal, the Zika virus and issues with the city's security, infrastructure and venues These are the Games of the 31st Olympiad but are the 28th to be held as those in 1916, 1940 and 1944 did not take place because of war. 
There will be 10,500 athletes from a record 207 teams competing in Rio, including the Refugee Olympic Team, while it will be the first time Kosovo and South Sudan have taken part in the Games. 
The Refugee Olympic Team will compete under the Olympic flag and has 10 members - five from South Sudan, two from Syria, two from DR Congo and one from Ethiopia. 
With 554 athletes, the United States has the largest Olympic team, but 100m runner Etimoni Timuani is the only athlete from the South Pacific nation of Tuvalu. 
The Rio Games will be the first to feature Olympians born since the year 2000 - and the youngest is 13-year-old Nepalese swimmer Gaurika Singh. 
The build-up to Rio has been overshadowed by events in Russia, after the World Anti-Doping Agency (Wada) report into state-sponsored doping in the country. 
On Thursday, the IOC cleared 271 Russian athletes from the country's original entry list of 389, though 67 of its 68 track and field athletes have been barred by the sport's governing body. 
Brazil has drafted in 85,000 security personnel from 55 countries who will be stationed at the sport venues, Olympic Village, airports and main roads - almost twice as many as were at the 2012 London Olympics. There is also 200km of security fencing being used. 
According to the BBC more than 500,000 tourists are expected to come to the Games and organisers say more than one million of the 7.5 million tickets remain unsold. 

Source ; QNA