A comprehensive investigation into state-sponsored doping in athletics has found the Russian Olympic team "corrupted the London Games on an unprecedented scale".
The final McLaren report, a seven-month inquiry led by Canadian law professor Richard McLaren, found their "desire to win medals superseded their collective moral and ethical compass and Olympic values of fair play".
Overall, it found more than 1,000 Russian athletes in 30 Olympic and Paralympic sports benefited from a state-sponsored doping cover-up between 2011 and 2015.
More than 1,100 items of evidence, a treasure trove of emails, forensic reports and lab analysis, back up the key findings of the explosive first report, which was published three weeks before the Rio Games.
Here's what you need to know.
What competitions were affected?
The investigation, funded by the World Anti-Doping Agency (Wada), found evidence that 78 Russian athletes at London 2012, including 15 medallists, had positive tests hidden by a Moscow laboratory.
Russia won 24 gold, 26 silver and 32 bronze medals in London, while no Russian athlete failed a drugs test at the time of the Games.
It is a similar story for the World Athletics Championships in Moscow, where four athletes had their positive samples swapped for clean ones.
And at the 2014 Winter Olympics in Sochi, 12 medal-winning athletes are among those implicated. Thirty sports, including football, were affected.
Is there any chance the report is wrong?
Not at all, the evidence cannot be contradicted.
Experts conducted three types of forensic analysis on samples.
These were, McLaren said: "The examination of selected B sample bottles for scratches and marks; the analysis of selected samples for unnaturally high or low salt content; and the examination of selected samples to compare the DNA in the sample with the DNA of the athlete who provided the sample."
The results were astonishing.
Two female ice hockey players at Sochi 2014, for example, had samples containing male DNA. Two athletes who won four gold medals between them in Sochi had levels of salt incompatible with humans in their samples.
Mclaren added:"The forensic testing, which is based on immutable facts, is conclusive."
How were they not caught?
Russia developed its ways of hiding and covering up positive tests as testing methods evolved.
They used salt and coffee to alter their samples, the report added.
"Our investigation has revealed that for every action from Wada there was a reaction," McLaren said, adding it is "impossible to know how deep and how far back" the conspiracy went.
What happens next?
Speaking at a news conference, International Olympic Committee (IOC) president Thomas Bach said the report's findings would be taken up by two further commissions.
He said the IOC would decide what steps to take when those commissions had made their recommendations.
Giving his personal view, he said athletes and officials who are proven to have been part of a doping "manipulation system" should be banned for life from the Olympics.
McLaren added: "We have shone a light on a dark secret...
"For years international sports competitions have unknowingly been hijacked by Russians. Coaches and athletes have been playing on an uneven field (and) sports fans and spectators have been deceived.
"It's time that stopped."