Formula One is poised for the climax of the closest title battle for 21 years.
This year will be the first three-way F1 title decider since 1986
McLaren drivers Lewis Hamilton and Fernando Alonso and their Ferrari rival Kimi Raikkonen all have a chance of winning the world championship at Sunday's Brazilian Grand Prix.
As championship leader, the Englishman has the advantage, but the battle between the three men is finely poised.
We analyse the factors influencing the title battle as the drivers begin their preparations in Sao Paulo.
Interlagos is one of F1's historic venues. It is steeped in atmosphere, and carries a unique challenge.
It held the Brazilian Grand Prix in the 1970s, and after an interlude at Rio de Janeiro's Jacarepagua track the race returned to Sao Paulo in 1990.
The track's first challenge is physical. It is fast and bumpy, and is one of the few circuits that runs in an anti-clockwise direction.
Drivers have built up their neck muscles to cope with circuits that have a predominance of right-handed corners, so they often have problems with fatigue around Interlagos.
Sao Paulo's Interlagos track presents a unique challenge
Hamilton is incredibly fit, so it is difficult to see that affecting him. But his two rivals have the advantage of knowing what they are in for.
The same goes for the circuit itself, although not knowing tracks has proved no barrier to success for Hamilton so far in his debut season.
Neither Alonso nor Raikkonen has won in Brazil before, although the Spaniard did clinch both his world titles there in 2005 and 2006.
Many tracks this year have favoured one of the top two cars over the other. But the McLaren and the Ferrari are expected to be evenly matched in Brazil.
The long straight and handful of fast corners will favour the Ferrari. But the McLaren is expected to cope better with the plethora of bumps and the tighter infield section.
Another potential advantage for McLaren is that tyre supplier Bridgestone will take its two softest compounds to Brazil.
Interlagos traditionally provides exciting, incident-packed races
Teams have to use both types at some point in the race. And the softer tyre should in theory provide crucial extra grip over one lap in qualifying.
But Ferrari have struggled to make the so-called "super-soft" tyre work on their car this season.
They have worked hard to combat that ahead of Brazil, but it remains to be seen whether they have succeeded.
Interlagos traditionally provides exciting, incident-packed races.
The track is short and fast. The long straight makes overtaking much easier than normal. The weather is hot and humid - and often wet, as well. The enthusiastic Brazilian fans and the crowded, frantic city provide a heady atmosphere. And the circuit's rough-and-ready nature means accidents are common.
That means the chances of any of the title contenders becoming embroiled in some sort of tangle - quite possibly with each other - are far higher than usual.
It is unlikely Hamilton has spent much time pondering the lessons of history, but if he had it might give him some sleepless nights.
The last three times there was a three-way fight for the title at the concluding Grand Prix, the man leading before the race did not become champion.
In 1986, Williams driver Nigel Mansell had a six-point lead over McLaren's Alain Prost heading into the Australian Grand Prix, with Mansell's team-mate Nelson Piquet also in the frame.
Mansell (centre) lost out in 1986 despite leading into the final race
But Mansell retired with a tyre failure while he was in the third place he needed to clinch the title and Prost won the race and his second crown.
That came three years after Prost himself had been disappointed. Then driving for Renault, he led by two points going into the South African Grand Prix in 1983 from Piquet, then at Brabham, with Ferrari's Rene Arnoux in with an outside chance.
The Brazilian romped away with the race, handing victory to team-mate Riccardo Patrese after Prost's hopes had evaporated with a turbo failure.
In 1981, Piquet himself benefited. He made up a one-point gap on Williams's Carlos Reutemann - despite finishing the race close to exhaustion in fifth place - thanks to the Argentine's famously inexplicable slump from pole position to finish seventh and out of the points.
There have been occasions when the man leading two rivals at the final race did become champion - but the last one was in 1968, if you do not count 1974, when Emerson Fittipaldi and Clay Regazzoni were tied on points.
The odds - and his position at the head of the championship - may be in Hamilton's favour, but it certainly goes to show that he can take nothing for granted.