China's Wang Han emerged as one of the youngest billionaires, when the value of his budget airline Juneyao tripled in value in less than three weeks this month. Although Mr Wang, 27, has an inherited net worth of US$1.2 billion (S$1.6 billion), he is counted among the newly-minted members of the billion-dollar club in 2015.

Here's a look at a few entrepreneurs who made it on their own to this elite club by putting their unique ideas to paper - or rather, to the Internet:

1. Evan Spiegel, 25, self-made; estimated net worth: US$1.5 billion

Evan Spiegel is the chief executive of Snapchat, the photo messaging company he cofounded in 2011 with Bobby Murphy, his senior in Stanford.

They met at a frat house and became friends, eventually developing an app that could send photo messages to contacts with a timer called Picaboo. It flopped. They rebranded it as Snapchat, and in 2011 the app took off and is now used by 100 million people monthly, for free. This year, two years after Spiegel turned down a US$3 billion offer from Facebook, Snapshot received offers for US$19 billion.

2. Elizabeth Holmes, 31, self-made; estimated net worth: US$ 4.6 billion

The death of an uncle from cancer because it was not caught early was the motivation for Elizabeth Holmes to start her blood testing company Theranos. Valued at US$9 billion now, the company has propelled her into the list of world's youngest female billionaires.

A dropout of Stanford University, Holmes launched the company that uses just a drop of blood for more than 70 different tests in a faster, cheaper and less painful way for testing. In 2013, Walgreens, the largest US retail pharmacy chain, announced plans to roll out Theranos Wellness Centers inside its pharmacies.

So far, there are 41 Theranos labs in California and Arizona. Board members of Theranos include elder statesmen George Shultz and Henry Kissinger

3. Travis Kalanick, 38, self-made; estimated net worth: US$5.3 billion

He is the chief executive of Uber Technologies, the hot ride-hailing service that has raised more than US$4 billion from investors. Uber is the third startup of UCLA dropout Kalanick, who is estimated to own at least 13 per cent of this company.

His first venture, an online file-exchange service, failed after which he filed for bankruptcy in 2000. His second company, a file-sharing company called RedSwoosh, was sold in 2007 to cloud computing firm Akamai Technologies for US$18.7 million in stock.

Uber has now been valued at a whopping US$41.2 billion. It is competing with taxi services across the world and plans to invest over US$1 billion in China this year.

4. Brian Chesky, 33, self-made; estimated net worth: US$1.89 billion

Co-founder and chief executive of Airbnb, Brian Chesky was a former bodybuilder studying at the Rhode Island School of Design. He started what was earlier known as Airbedandbreakfast.com in San Francisco with Nathan Blecharczyk in 2008, a peer-to-peer home and apartment rental firm, which was valued in April 2014 at US$10 billion after an employee stock sale.

As of early 2015, 30 million guests had used the service which has nearly 1 million homes listed on its site.

5. Markus 'Notch' Persson, 36, self-made; estimated net worth: US$1.34 billion

Known online by his nickname Notch, Markus Persson - the son of a nurse and a railroad worker - grew up relatively poor, but hit it rich when he developed a hobby project into the most-downloaded computer game: Minecraft.

Persson worked on the Lego-like graphics of the game while working at Candy Crush maker King Entertainment, but quit when the game gained popularity and eventually formed his firm called Mojang. The company sold 1 million copies of Minecraft by January 2011 and has sold more than 100 million copies across platforms including PC, iOS, Android, Xbox and PlayStation to date. In September 2014, Microsoft purchased the Stockholm-based company for US$2.5 billion.

6. 'Brian' Kim Beom-Su, 49, self-made; estimated net worth: US$2.3 billion

A Korean slumdog millionaire tale. Born to parents who did not finish grade school, Kim grew up in poverty in a one-room shared apartment, paid his way through school by offering private tuitions and sometimes skipped meals to save money. An industrial engineer by degree, his first employer was Samsung.

He founded an online gaming company in the late 1990s which merged with another Korean outfit to dominate the country's search and web traffic. When smartphone arrived in 2009, he grabbed on the opportunity to create a messaging service KakaoTalk.

Soon a team was working for him to create games and apps that would make users dependent on the platform and eventually allow it to generate revenue. New services like KakaoPay, BankWallet Kakao and KakaoTaxi are in the offing.

SOURCE: Forbes, Reuters