How on earth can she be seventy-one-years-old?!

In a recent I Am Cait reunion, which was released on her birthday, people cannot get over how incredible Caitlyn looks for a woman of her age.

Now, Caitlyn first rose to fame as one of the most beloved athletes of the '70s...

So maybe all that exercise could explain it? The gold medal-winning track star set a world record in the decathlon at the 1976 Summer Olympics in Montreal, scoring a staggering 8,634 points.

Following her Olympic success, she has remained well and truly in the spotlight.

This was maintained through a number of TV appearances and endorsements, Jenner remained in the public eye. From the late '70s to the early '00s, she worked on several tv series and appeared in a handful of movies.

But there's another thing Caitlyn is very well known for...

And that's Keeping Up With The Kardashians, of course.

Caitlyn became a huge part Keeping up with the Kardashian's.

She came into Kris's life after the death of her first husband, Robert Kardashian. She had 2 children with Kris (Kendall, and Kylie) and was hastily blended as a significant role model to all the Kardashian sisters.

And, of course, we all know about the famous Caitlyn Jenner transformation.

via: Getty

Jenner initially announced she would be beginning her transition back in 2015 - and even launched her own reality show titled I Am Cait, chronicling her journey throughout her transition.

2 years later, in true Kardashian-Jenner fashion, she went public on the cover of Vanity Fair.

She underwent her final operation - the gender-reassignment surgery - in 2017.

And she couldn't be happier.

In her debut Vanity Fair interview as Caitlyn, she explained how liberating it felt to finally be open as a woman: "I have nothing left to hide. I am kind of a free person, a free soul. Up to this point, I would wear, you know, Bruce would wear sweatshirts with hoods on them so paparazzi can’t get pictures and all that kind of crap."

Caitlyn insists that she is a nicer person than ever now she has transitioned.

When asked about sending a full airplane out just to pick up her Mom, Caitlyn explained: "I know. What I told her: 'Isn’t Caitlyn a much better friend?' Bruce, he would never send a plane. No, no, no, what a jerk the guy was, O.K., Caitlyn is like, 'Send the plane. Mom, we’re sending a plane, we’re going to go pick you up and bring you down here.'... It seems like she has a lot more friends than he ever had."

Yet, despite Caitlyn being happier and more popular than ever...

Her transition understandably took its toll on her daughters, Kendall and Kylie. "My dad says it herself sometimes, it's kind of like mourning the loss of someone, because it is," Kendall said in a candid interview about Caitlyn's transition. "My dad is my dad, but he’s not there physically anymore. But she lets me call her dad - that's the last little piece of dad I've got."

Though Kendall insists that she'd known about Caitlyn's gender identity for years.

"It's an adjustment. It's something you have to get used to. But I've known since I was a kid," Kendall revealed in the same interview. "She never confirmed it to me, but I’ve known for a very long time. It's the same person."

There has been a noticeable strain in Caitlyn's relationship with her daughters.

And Kendall has remained loyal to her mom, Kris, during her parents' feud. "Kendall is loyal to Kris [Jenner] and has very little to do with her dad. The more time that has passed, the more she feels Caitlyn has let her down with the things she has said and with her actions," a source shared with E! back in 2017.

Well, it's been a few years since her transition now...

And even though they have been through some pretty rough patches, the family seems to have worked things out.

Caitlyn prides herself on using her celebrity status to spread a positive message of tolerance.

“If there is one thing I do know about my life, it is the power of the spotlight," Jenner said. “Sometimes it gets overwhelming, but with attention comes responsibility," she explained during her EPSY awards speech, in which she received the Arthur Ashe Award for Courage.

She continued:

"As a group, as athletes, how you conduct your lives, what you say, what you do, is absorbed and observed by millions of people, especially young people. I know I’m clear with my responsibility going forward, to tell my story the right way — for me, to keep learning, to do whatever I can to reshape the landscape of how trans issues are viewed, how trans people are treated. And then more broadly to promote a very simple idea: accepting people for who they are. Accepting people’s differences."

She is passionate about paving the way for trans kids.

via: Getty

"If you want to call me names, make jokes, doubt my intentions, go ahead because the reality is, I can take it. But for the thousands of kids out there coming to terms with being true to who they are, they shouldn’t have to take it."

Overall, Caitlyn is one hell of a woman...

And she deserves to be celebrated... especially on her birthday.

Yep, as stated earlier, the reality star turned seventy-one yesterday.

Youngest daughter, Kylie, shared this heartwarming selfie on her Instagram Stories, writing: "Happy birthday @caitlynjenner, love you so much."

Kendall, however, opted for a more retro tribute.

She shared this throwback pic to her Stories, writing simply: "Love you!"

But, putting the family tributes to one side...

People are talking about something else entirely.

Just before her birthday, an I Am Cait reunion was posted onto YouTube...

And people are marvelling at how incredible Caitlyn looks for seventy-one.

For the 5 year anniversary of her debut reality show, Caitlyn invited the girls she'd first filmed with to sit down, have lunch, and reminisce.

They discussed a whole array of topics, including the issues still surrounding the LGBTQ community today.

But let's just stop for one second...

How does Caitlyn look so damn young?!

Many were quick to notice that Caitlyn was simply glowing...

Which is a lot more than most people nearing their seventies can say.

Maybe it was all that wine?

If so, I'm set for eternal youth. You can watch the reunion video above. For more on Caitlyn, keep scrolling to hear why none of her family told her about the end of Keeping Up With The Kardashians...