Aly Raisman was the captain of the "fierce five" in London in 2012.
Raisman led the women's gymnastics team in London in 2012 and she's back this year along with Gaby Douglas. Together, they are the first American women since 2000 to make back-to-back Olympic gymnastics teams.
On Instagram, she shows off her artsy leotards and a sock line that she's designed.
Simone Biles will be making her Olympic debut this summer.
She and fellow teammate Aly Raisman are close friends, dubbed "Grandma Raisman" and "Baby Simone."
Biles is the three-time world all-around champion and a favorite for this summer. Her teammates say she's always full of energy and her Instagram affirms that. You can also follow her on Snapchat to see her journey: simonebiles.
Gabby Douglas made history in 2012 when she became the first African American woman to win gold in the individual all-around.
Now she has her own TV show, a line of emojis, and her own Barbie doll, all while prepping for Rio. She isone of the first American women since 2000 to make back-to-back Olympic gymnastics teams, along with her teammate Aly Raisman.
You can keep up with her busy life on Instagram or see more of her and her family on Snapchat: gabbydoug.
Sam Mikulak is a member of the men's gymnastics team. He's returning to the Olympics for a second time.
If Mikulak isn't in the gym, he's hanging out with his family, other athletes, or connecting with fans over his brand MateBros. Rio will be the second Olympic games that the 23-year-old competes in.
His Instagram has a lot of posts about his branded drinks and t-shirts but also gives an inside peek into his training, his Snapchat continues the fun: sammikulak
Jake Dalton has a YouTube channel he uses to keep up with fans.
Dalton is 24, and this will be his second Olympic games. He went to University of Oklahoma for four years where he met his wife Kayla who was also a gymnast there.
In addition to his YouTube channel, he posts on Instagram, and on Snapchat: JAKEOU.
Michael Phelps may break more records this year in Rio — you'll want to see it.
Phelps made his Olympic debut in 2000, but he didn't medal until Athens four years later. Rio will be his fifth Olympic games, where he'll compete to up his 22 medal count.
The world has watched him go from 15-year-old teenager to now a 31-year-old husband and father. To stay up to date on Phelps potentially making history again, follow him on Instagram.
Ryan Lochte was an all-American heartthrob at the 2012 games.
The 11-time Olympic medalist had a short stint as a reality TV star on his show "What Would Ryan Lochte Do?" so he's used to being on camera.
Now he sticks to Snapchat as ryanlochte. He also updates his Instagram pretty frequently.
Missy Franklin was one of the most decorated athletes at the 2012 London Olympics.
Though she was one of the most decorated athletes at the London Olympics, in many ways, she's still a typical college student: Franklin attends UC Berkley and loves to hang out with her friends and have fun.
But she's also an Olympic athlete who trains hard, as her Instagram shows.
Elizabeth Biesel was just 15 when she competed in her first Olympic games in China.
Biesel is a Rhode Island native who made the national swim team when she was only 13 years old. Her mother swam for the University of Rhode Island when she was in college and passed her love for the sport on to Elizabeth.
Follow her journey to her third Olympic games on Instagram.
Serena Williams has been one of the biggest names in Tennis since she was a teen.
This summer she'll be playing doubles with her sister Venus and singles at the Olympics, continuing her reign as one of the best players in the world of tennis.
Williams has an Instagram and you can also follow her on Snapchat (SerenaUnmatched) where she's always using the newest filters and showing off her outfits for her next match.
Her teammate Madison Keys is the rookie of the USA Women's Tennis team this year.
Keys is just 21 and has been making waves in the tennis world since she went pro at the age of 14. She is now ranked in the Top 10 of American female tennis players, coming in third place behind Serena and Venus Williams.
Rio will be her first Olympic games, and you can follow her prep on Instagram.
Demarcus Cousins has played for the Sacramento Kings since 2010, but this will be the first time he represents Team USA at the Olympics.
He's 6'11 and has come under fire for his high technical foul count throughout his career, but is a solid athlete on the court. This is his first year in the Olympics.
Cousins updates his Instagram regularly, and sometimes even posts pictures of his adorable son Amir. You can follow him on Snapchat to see more, boogiecousins.
Breanna Stewart has had a big year, from UConn, to the Seattle Storm, to Team USA.
Stewart played for the University of Connecticut and won the NCAA Tournament every year she played. She was then recruited by the Seattle Storm to play in the WNBA. She's now heading to Rio just a few months after graduating college and signing her professional contract.
It's safe to say it's been a big year for Stewart — and she's documented it all on her Instagram.
Draymond Green is a rookie to the Olympics although he has played in international tournaments for the USA before.
Green graduated from Michigan State where he played for a full four years before joining the NBA as part of the Golden State Warriors. This will be his first Olympics, although he has played for the national team before.
You can follow him on Instagram to see how his journey is going and on Snapchat as money23green.
Nia Ali made a huge comeback after having a baby with fellow Olympic hurdler Michael Tinsley.
Ali had never made an Olympic team until this year and now she's headed to Rio with her best friend Brianna Rollins. She had to bounce back quickly after the birth of her child, but she's ready to take on the world in Rio.
She posts updates and pictures of her son Titus on her Instagram.
Mikaela Mayer aspired to be a model before she found her passion for boxing.
Mayer didn't start boxing until she was 17. She failed to qualify for the 2012 Olympics, but now at age 26, she's heading to Rio.
She travels a lot and posts frequently on Instagram and Snapchat where her username is mikaela.mayer.
Maxwell Holt is the center blocker for the USA Volleyball team.
Holt graduated from Penn State in 2009 with a degree in journalism and went on to play volleyball in Russia. This summer will be his first Summer Olympics, though he was an alternative in 2012 for Team USA.
You can follow Holt on his Instagram.
Kerri Walsh Jennings has gone gold at the past three Olympic games.
This year, she has a new partner, but is just as ready to play. She attended Stanford University on a volleyball scholarship and has had a wildly successful career since.
To find out how Jennings feels about taking on the Olympics for a fourth time, follow her on Instagram.
April Ross is partners with Walsh Jennings for beach volleyball this summer.
During the last Olympic games Ross lost the gold medal to Walsh Jennings. This year, the pair are hoping to win gold together.
The two are doing plenty to prepare for the games and Ross updates her Instagram and Snapchat almost daily — follow her at AprilRossBeach.
Steele Johnson started diving lessons because his parents were worried he was going to get hurt teaching himself to do flips off of diving boards.
Johnson is a student at Purdue University who has been diving from a young age. He will be competing this summer in his first Olympics in the 10-meter individual and synchronized with David Boudia, a friend he's been training with since he was nine or 10.
His Instagram is full of team USA pride and he Snapchats too at steele_johnson.
Jordan Burroughs withdrew from the Freestyle World Cup in early June to be at the birth of his daughter.
Burroughs won gold in London in 2012 and he's coming back this year to try for it again. He's a proud father and three-time world champion.
His Instagram bio says, "You are now watching history in the making."
Adeline Gray is a three-time world champion freestyle wrestler.
This summer will be her first Olympics, although she's no stranger to high-stakes matches. She started wrestling at a young age and has used her platform to encourage young girls to dream bigger.
Watch her take on the Olympic games with updates from her Instagram.
Kayla Harrison was the first American athlete to win a gold medal for Judo.
Harrison made history in 2012 and she's heading to Rio to defend her title as the Olympic champion. Her career has been fraught with challenges, but she's used her status to help create change.
Follow her story on Instagram.
Mattie Rogers started weightlifting at the age of 18 after she started doing CrossFit.
She may go by Mattie Rogers, but this athlete's real name is Martha. The Rio Olympic games will be her first.
To see her lift incredible weight, check out her Instagram, and she's also very active on Twitter.
Madison Hughes is a big name in the game of rugby.
The Dartmouth graduate is a leading scorer in the HSBC Seven Series. He's joining several other Olympic veterans who will fill out the team of 12, in addition to a New England Patriot's player.
Follow Hughes and his team on Instagram.
Alex Morgan became a household name after the 2012 London Olympics.
Team USA won gold in 2012 and Morgan was named female athlete of the year by US Soccer for her standout season. She plays for the Orlando Pride during the year and is heading to Rio this summer with the rest of the team.
See it all unfold on her Instagram.
Dagmara Wozniak was born in Poland but moved to the United States with her parents when she was one.
Wozniak placed eighth in the individual competition in London and is returning to the Olympics this summer again with Team USA. She's currently ranked number one in the USA and 12th in the world.
She's been fencing for nearly 20 years — follow her quest for gold on her Instagram.