At the end of judo competition on Saturday, eight medals will be awarded. At least one of them could go to the host nation.
Sarah Menezes, the reigning Olympic champion in the women's 48kg (106 lbs) division, could become Brazil's first medalist of the Rio Games. She's the No. 4 seed in the tournament and will have the backing of the home crowd behind her.
This will be the third Olympics for Menezes; she lost in the first round in her Olympic debut in 2008 before taking gold in 2012.
At the World Masters tournament in May, Menezes ended up with silver after losing to Japan's Ami Kondo in the final round. Kondo, the No. 3 seed, will be on the opposite side of the bracket along with No. 2 seed Paula Pareto of Argentina.
The biggest obstacle for Menezes could be a potential semifinal match against Mongolia's Urantsetseg Munkhbat, the world No. 1.
Here's what else to know for the opening day of competition.
The first block will feature preliminary and quarterfinal matches, and will take place on two separate mats, each with a dedicated live stream.
The final block will feature repechage matches, semifinals, Bronze Medal Matches and Gold Medal Matches.