The female Mark Zuckerberg: How 21-year-old created a social network because she didn't like her school yearbook photo... and is now worth $20m

Catherine Cook and her brother David were complaining about the choice of photographs in their annual school yearbook when an idea struck.

She set up a social networking site using a computer in her bedroom and in six years has built up 25 million users across the United States.

Myyearbook.com is one of the top 25 most visited sites in the country - and Miss Cook's company has just been valued at $20m.

Catherine Cook: The millionaire internet entrepreneur is now a student at Georgetown University

Her success has already brought her comparisons with Facebook founder Mark Zuckerberg.

'It all happened so quickly,' she said. 'One minute we were brainstorming ideas, the next we had received an investment of $250,000.

'My older brother Geoff had already enjoyed success with another website and decided to invest in us.'

Speaking about the inspiration for the idea, she said: 'I remember the day we were given our yearbooks at school. It was 2005 and my brother David and I were moaning how much we hated our photos.

'He said, "What if we could choose our own photo?" and I said "What if you could interact with other people online?" then it just went from there.'

There are various features on the site that make it much more complex than Facebook, not least the ability to vote on a popularity leaderboard.

Myyearbook: Catherine's page on the site which grew after recommendations from her schoolmates were incorporated into the website

'We had to draw out every page by hand. Then we found a development team in Mumbai, India. It was all very exciting, but we were still in high school and the hours were getting really long.

'I started burning the candle at both ends, working on my school work all day, and then staying up till 4am talking to Indian developers.'

Despite her success, Catherine keeps her feet on the ground and insists it is a family business

Catherine and David launched the website from their home in Skillman, New Jersey, in April 2005. 'My mom and dad are both electrical engineers, but we did all the work ourselves.

'We promoted the site at school, wearing crazy T-shirts around campus.

'Next we allowed the site to be joined by members of all schools nationwide in November of 2005, just months after launching.

'When we got to one million I remember feeling so excited, yet so scared. Live was changing in ways I could never imagine.'

By 2006 the pair of internet entrepreneurs had outgrown their bedroom and they invested in a state-of-the-art office building in New Hope, Pennsylvania.

Aged just 16, Catherine had a staff of 12 new developers.

'Looking back I was only getting two hours sleep a night. It was hard to manage school and work, but soon afterwards I graduated from high school, and just as the business was taking off I realised my personal life was suffering too,' she said.

Her relationship with her high school boyfriend came to an end.

'I knew he was going to another university, and I knew we wouldn't be able to see each other.

'He'd been so supportive of me, hanging around while I sat up all night working on the site. But I knew when I went off to Georgetown that it would be the end of our relationship.'

Catherine was also the victim of jealousy, similar to that felt by Zuckerberg.

She explained: 'Once the site became an overnight success, there was a weird situation with a guy in my Spanish class.

'We were friends but he suddenly stopped speaking to me. It turned out his parents had given him a hard time, telling him "How can she launch this social network and you can't even keep your grades up?".'

Catherine was a speaker at a social network conference where Mark Zuckerberg was the headliner

She was even told that she would never compete with MySpace - she now has a quarter of their number of visitors and employs 100 people.

Speaking about why she thinks the site is a success, Catherine said: 'Most of my friends were really into the idea. They'd join the site and make suggestions: "you should be able to give people high fives," they said, or suggested gold stars instead of "likes".

'I even met my best friend through the site. She said me a message saying, "I think you're my neighbour." We've been best friends ever since.'