Attractive, clever, and rich, rich, rich, these 13 individuals are the youngest billionaires in the Bay Area, according to the most recent figures from Forbes. Twelve of them share three things in common: their fortune is self-made (they didn't inherit it), they made their money in tech, and they're all male.

But who is the one exception?

Featured in October's "Hot 20" list, Elizabeth Holmes is CEO and Founder of Theranos, a Palo Alto-based consumer healthcare technology company that is revolutionizing blood testing. Forbes has valued the 30 year old's net worth at $4.5 billion, making her the youngest woman on the Forbes 400.

Topping our list of the Bay Area's youngest billionaires is, naturally, Facebook's Mark Zuckerberg, with a net worth of $34.8 billion. Facebook is responsible for three others on the list: Dustin Moskovitz ($8.2 billion), Jan Koum ($7.7 billion), and Sean Parker ($3.1 billion.)

Following this year's phenomenal IPO of the company he founded, GoPro, Nicholas Woodman is 4th on the list with a net worth of $5.1 billion.

Uber founder Travis Kalanick is also a new billionaire thanks to the extraordinary valuation of his company. He's worth $3 billion today (more during surge hours.) And the so-called "sharing economy" has produced three other billionaires -- the founders of AirBNB, Joe Gebbia, Nathan Blecharczyk, and Brian Chesky, are each worth $1.5 billion.

Robert Pera became a billionaire in 2011 when his wireless networking company, Ubiquiti Networks, went public. He's worth $2.3 billion, and used some of his fortune to purchase the Memphis Grizzlies NBA franchise.

And finally, at the bottom of the list, is Drew Houston. The founder of Dropbox is worth $1.2 billion -- a mere drop in the bucket (or is that a box?) by billionaire standards, he doesn't even qualify to be on the Forbes 400! Better luck next year, Drew!

Bay Area Billionaires Under 40

1. Mark Zuckerberg (30), $34.8 Billion

2. Dustin Moskovitz (30),  $8.2 Billion

3. Jan Koum (38), $7.7 Billion

4. Nicholas Woodman (39), $5.1 Billion

5. Elizabeth Holmes (30), $4.5 Billion

6. Sean Parker (34), $3.1 Billion

7. Travis Kalanick (38), $3 Billion

8. Jack Dorsey (37), $2.6 Billion

9. Robert Pera (36), $2.3 Billion

10. Joe Gebbia (33), $1.5 Billion

11. Nathan Blecharczyk (32), $1.5 Billion

12. Brian Chesky (33), $1.5 Billion

13. Drew Houston (31), $1.2 Billion