Today Google Photos has more than a billion users. Most of those users probably don’t know that Google Photos' story begins at a startup called Bump — part of YC’s Summer 2009 batch.

Bump was a mobile app used by more than 150M people to share photos and contact info by bumping their phones together — something that, at the time, was an absolute game changer. Bump was acquired by Google in 2013, and an unreleased photo sharing app they were building became the foundation of Google Photos.

David Lieb, Bump’s CEO and co-founder, led the product from inception all the way past the billion user mark. And today, after three batches as a Visiting Group Partner at YC, he is our newest full time Group Partner. I’m so proud to welcome him.

Just as mobile unlocked new ideas like Bump, today we’re seeing AI unlock an entirely new wave of consumer companies. Google Photos might be the very first example of this — a mass consumer product built with AI search, face recognition, and editing at its core. Dave is an expert at knowing how to use AI to make something people want. Having him on your side to help navigate this new world is an incredible advantage.

As an advisor, he often reminds me of PG and Jessica, who brought founders back to the basics again and again. He pushes founders to focus on the things that matter. Who are you building this for? Not the imaginary silhouette of a customer — the real people, with names you know, that want this. And when did you last talk to them? As a founder, he admits that he let himself get distracted with big-name investors and app store ranking. Today, he can say with authority that nothing ranks higher than your customers coming back to your product again and again.

When Dave was interviewing for YC back in 2009, PG put his head down in the middle of the interview. He looked up and asked how Bump would be bigger than Google. It was this simple question that honed Dave’s focus and made his ambitions grow. We are so thrilled Dave has come back to YC to also encourage founders to think big.

Hear more about how Dave transformed his app into one of the biggest photo services in the world on The Social Radars.