The CEO of multibillion-dollar Pinterest knew he was onto something when he started getting personal emails from panicked users

Hollis Johnson/Business Insider

Pinterest CEO and cofounder Ben Silbermann.

• Pinterest CEO and cofounder Ben Silbermann started conceptualizing Pinterest, an image-search and sharing tool, in 2007.
• Today, Pinterest has 250 million active users and is valued at $12.3 billion, according to The New York Times.
• Silbermann said he realized how popular the tool had become when users would email him directly whenever the site went down.

Word spread about the early days of Pinterest, an image-search and sharing tool, similarly to how it does now: by its active and dedicated users.

Users were so dedicated, in fact, that if the site went down early on, CEO and cofounder Ben Silbermann would receive emails from users addressing the importance of getting the site up again, he said on an episode of Business Insider's podcast "This Is Success."

"When it would go down, because sometimes it would go down, people would write to us and they would say, 'Hey, Pinterest is down. I'm really depending on this to redecorate my home or to plan out my wedding,'" Silbermann said. He said these emails helped him realize how valuable the site had become to users.

Today, Pinterest has 250 million active users and is valued at $12.3 billion, according to The New York Times.

Read more: Pinterest overhauls its ad platform

Silbermann started conceptualizing Pinterest's software in 2007 while he was working at Google. He connected with Evan Sharp, a then-architect student in New York who collected pictures to aid his studies, which gave the pair an idea to create a virtual space where users could collect images and browse through other user's collections.

Silbermann said, "the most common way that people would hear about Pinterest, and the most common way they hear about it today, is somebody would do something. They would throw a party, or they'd redecorate their home, or they'd cook a special meal. And their friends would say, 'Hey, where'd you get the idea?' And they'd say, 'Oh, I got that idea on Pinterest.' Then they'd say, 'Oh, what's Pinterest?' And they'd try it out and download the app."

When Silbermann and Sharp were building their early audience, many users came from the midwest where the cofounders grew up - Iowa and Pennsylvania, respectively.

He said these initial users were not your typical "early adopters" of tech. "They weren't the kind of people that had the newest phone or downloaded everything. They were using it because it was really useful in their everyday life."

Listen to the full episode and subscribe to "This Is Success" on Apple Podcasts or wherever you listen.