Olympic Moments: Highlights From Day 2

Katie Ledecky celebrates winning gold and setting a new world record in the women's 400m freestyle final. She won with a time of three minutes, 56.46 seconds breaking the existing world record - her own, set in 2014 - by about two seconds.

Gold medalists Nathan Adrian, Ryan Held, Michael Phelps and Caeleb Dressell during the medal ceremony for the final of the Men's 4 x 100m freestyle relay. It took the team three minutes, 9.92 seconds to win.

Serena and Venus Williams during their match against Lucie Sarfarova and Barbora Strycova, of the Czech Republic. The sisters lost in straight sets marking their first-ever Olympic loss as a duo.

Maria Ribera of Spain carries the ball under pressure from Irene Otieno of Kenya during the women's pool B rugby match.

Brittney Griner (L) and guard Sue Bird (R) defend against Senegal's Maimouna Diarra during a women's round group B basketball match.

Simone Biles competes in the qualifiers for the women's floor event of the artistic gymnastics.

Emma Tonegato of Australia scores as she is tackled by Leyla Alev Kelter.

Michael Phelps, right, Danila Izotov of Russia, Kyle Chalmers of Australia, Yuri Kisil of Canada and Jasper Aerents of Belgium compete in the final of the men's 4 x 100m freestyle relay.

Lucie Safarova and Barbora Strycova celebrate after their win.

Taiwan's Tan Chi-Chung competes during the men's 56kg weightlifting event.

Venus Williams bawls after losing a point in a doubles match with her sister Serena against the Czechs.

Surinam's Evita Leter competes in the women's 100m breaststroke heats.

Lucie Safarova and Barbora Strycova of Czech Republic celebrate after winning their match against Serena and Venus Williams.

Michael Phelps celebrates during the men's 4 x 100m freestyle relay.

Gerek Meinhardt (L) competes against France's Erwan le Pechoux during the men's individual foil qualifying bout.

Dustin Brown of Germany reels in pain after being injured during his match against Thomaz Bellucci of Brazil.

Full Coverage: Rio Summer Olympics

United States' Aly Raisman performs on the balance beam during the artistic gymnastics women's qualifications.

Khatuna Narimanidze of Georgia prepares to shoot during women's archery 1/8 eliminations.

Bronze medalist Leah Smith, gold medalist Katie Ledecky and Silver medalist Jazz Carlin of Britain during the medal ceremony for the women's 400m freestyle final.

Simone Biles of the U.S. hugs team member Aly Raisman as Raisman gets her score during the women's qualifications.