Maya Peterson was only 9 years old when she sold one of her beloved American Girl dolls and used that money to buy stock in the company that makes the popular dolls.

Six years later, she still owns that Mattel stock. What's more, she continues to invest regularly in companies she researches, building an impressive investment portfolio along the way.

Now, Maya, 15, wants to share her insights about investing with other young people. Her recently released book, "Early Bird: The Power of Investing Young," offers investment tips and stresses the importance of getting a head start on investing.

"A lot of people think you need to have tons of money to make a difference," said Maya of St. Paul. "They think you need to be Bill Gates or Warren Buffett, which is very untrue. Even the $20 that you got for mowing your parents' lawn is quite a lot of money and can make a difference in the long run."

The Mounds Park Academy freshman wrote the book over several months, culling material from her investing blog, "Compounding Snowballs," and from interviews she conducted with seasoned investors.

Before becoming a young author, Maya read finance books. One book in particular, called "Growing Money," shaped her understanding of finances.

Maya Peterson, 15, wrote an investing book for young people.

"It described the simple mechanics of investing," said Maya, who noted that the book introduced her to such concepts as compound interest and inflation.

But what really hooked her, she said, was a question posed in the book: Would you rather have a million dollars now or a penny that doubles every day for 30 days?

Once she realized that the penny that doubles every day would grow to be $3 million dollars, she grasped a key principle of investing: time matters.

Soon, Maya was traveling with her father — who works in software design — to Omaha every year to hear Buffett speak at the Berkshire Hathaway annual shareholders meeting, standing in line at 4:30 a.m. to get into the meeting.

Always precocious, Maya was 7 when she first got started in business. She made earrings and sold them at a local store.

"Money was always of interest," she said, "and getting more money, of course, so I could spend it."

When she grew a little bit older, she started a small summer camp for kids with a friend.

"We were trying to think of a way to babysit, but to our advantage where we could pick the price and we could pick how many people and the times, so that we could schedule it in a way that worked for us," Maya said.

When she was in fifth grade, she applied for the Motley Fool College Women and Investing Program. She became the youngest person accepted for the conference, and flew to Washington, D.C., to attend and visit the Motley Fool headquarters.

She also helped them develop a course for schoolchildren to teach them about investing.

Her passion for numbers and investing is matched only by her yearning to share what she's learned with others.

At school, her peers have been supportive.

"I'm lucky to be at a school where nerds are valued," she said.

And she's inspired a few of her friends, who've recently been bitten by the investment bug.

"They seem to enjoy it," Maya said. "It's always fun to have people who you can talk to about it."

Allie Shah • 612-673-4488

Twitter: @allieshah