At just in her early 20s, the Kardashians' Kylie Jenner has become a social media superstar and built a cosmetics brand, surpassing Bill Gates and Mark Zuckerberg to become the youngest white-collar billionaire ever.

Here's her revealing story after becoming the fourth youngest person on the list of richest American women from nothing in 2018.

Jenner's company has only seven full-time and five part-time employees, and she outsources most of her business.

She attributes her success to social media such as Instagram. She has a large social media following, mostly of young girls.

Just as her half-sister Kim Kardashian had buttock surgery, Jenner has had lip augmentation surgery.

Like Kim Kardashian, she has used her assets to gain fame and money.

Just 20 years old in 2018, Jenner is a very young mother (she gave birth to her youngest daughter, Stormi, in February) and runs one of the hottest makeup companies of all time.

In 2016, Kylie Cosmetics launched its "Lip Kit" for $29, which included a matching set of lip glaze and lip liner.

Since then, the company has sold more than $630 million worth of makeup, including an estimated $330 million worth in 2017.

In addition, she is conservatively estimated to be worth $900 million, considering that she has made millions from TV shows and endorsements.

Combined with her age, she is the youngest person to reach the fourth spot on the list of richest American women from nothing.

By comparison, Forbes estimates that 37-year-old Kim Kardashian is worth $350 million.

But she's not just making female history. In another year, she is on track to become the youngest billionaire ever to start with nothing, trumping Mark Zuckerberg's record of 23 years old.

At the end of the day, their fortunes all come from the same place: social media.

Social media is an amazing platform," says Jenner. It's very easy to connect with fans and customers."

In short, what Jenner does is use her social media following to make money.

Almost every hour, she opens Instagram and Snapchat and takes a pouting selfie with a caption explaining which Kylie Cosmetics products she's using in the picture or makes a video promoting a new product that's coming out or has already been launched.

This may sound silly, but she has over 110 million followers on Instagram and even more on Snapchat, all of whom are young women and teenage girls who are the target audience for products like lipstick in large numbers.

In addition, 16.4 million people follow her brand account and she has a Twitter following of 25.6 million.

Her older siblings and friends also occasionally help promote the brand on social media.

Indeed, this is the nature of celebrity endorsements.