Where might you want to search that Google can't reach?  The social slice of the Web, plus everything that an individual has password-protected hovering in the cloud, has been largely off-limits to traditional search engines. Well, until an Israeli high-school graduate took a hiatus from Army duty to spend three months at Y Combinator, bombed on a few projects, and then struck gold in his last 48 hours at the start-up incubator. Daniel Gross, along with co-founder Robby Walker, 27, created Greplin, a user-authorized search that can access Facebook, Twitter, Google Documents, Salesforce, and more. The site launched in late February. Inc.com's Christine Lagorio spoke with Gross, age 19, about his struggles, raising nearly $5 million in investment after just six months at work, and his unique lack of college experience.

Tell me how Greplin came about.

I'm originally from Israel. I was in Israel and had graduated high school, and I was all set to go into the Israeli Army. I applied to Y Combinator. And not thinking I'd get in, I was invited to an interview. I thought of it as a fun long weekend in San Francisco. They had an odd reaction—they didn't quite like what I was working on, but I guess they liked me. They wanted me to come back, so I hopped back on a plane.

In my three months there, I built several things, none of which caught on. Right at the end of Y Combinator, you get a cool opportunity to get up on a stage and show your project to the world. And our project had just got shut down, so this was 48 hours before the end of the program. I went over to [Y Combinator co-founder] Paul Graham's house, and he said, "Just build something that you'd want to use today, not something you think people could use somehow." So I created a very, very, very basic demo in that 48 hours.

I got a weird reaction. I was a disheveled 18-year-old kid. But the idea had support. So I spent the next months building a workable product by night and raising $780,000 in angel funding. It was from a pretty cool team, the guy who made Gmail, Paul Buchheit, and Chris Dixon, and the guy who did Square. Also the CTO of Facebook, Bret Taylor.

Was there an "a-ha" moment in deciding on working on a search engine for peoples' online documents and social media files?

I had this very long list of things I thought would be cool. Greplin was always near the top. But my mistake at Y Combinator was not listening to my own intuition enough. There's the line "Wouldn't it be cool if this thing existed?" but those aren't often good ideas, because you're not the ideal user. It's also very hard to make a product when you're not the target audience. Because you have to make decisions along the way, and unless you would be the target user, you're going to make the wrong decisions. Understanding that fact was my "a-ha" moment. Greplin was the one project idea I had for which I was the target audience.

Where does the name come from?

The idea came way before the name. The idea was in a sense a headline: A search engine that lets you find all of your stuff online. This guy Adam Goldstein [cofounder of flight-search start-up Hipmunk] and Paul Graham were sitting with me. Adam just threw out this name. And using the word grep, which in CS programming is essentially a command for search. So a lot of nerds get that. Adam threw out the name, and people liked it.

It's also a good one because people can pronounce it, spell it over the phone, and has a backwards inside joke that you'll only get if you a technical person. Total win.

Did you ever have to slow down and think: Wait, what am I doing?

Well, once, and it was wise. More or less, we had some money in the bank and we launched the product. But we had this weird problem where we didn't know so many people would use it. I mean, a lot did. Somehow the code I'd written at 4 a.m. trying to get onto stage didn't scale very well. (Laughter.) At that point you can either monkey-patch everything, or you can start from scratch. We chose to do the latter. So we spent September through last month reworking it all.

And you just launched the site officially last week?

Yeah, we raised $4 million from Sequoia in December, and kept programming, and then just lauched the site, and we're trying to keep it growing since.

You say you're not trying to compete with Google, but what you've created seems a lot like Google for social media and cloud-computing. What portion of your data lives, personally, is in the cloud?

I had this realization a few days ago when I thought I lost my laptop. Then I realized I don't think I have a single piece of information that's solely on my laptop. I think I'm indicitive of a future generation.

You told the Wall Street Journal "We're Switzerland; we're neutral." What does that mean?

I think what I was trying to say is that if you look at a product like this, it's useful. There's a need. And the question is why hasn't someone built it already? The answer is that Apple, Facebook, LinkedIn, etc., they're not able to get access to the data other than your own. Google and Apple compete. They're not sharing data anytime soon. We're Switzerland, because any company creating a product like this cannot be biased to any product over another.

Do you think you'll go to college eventually?

The way it works in Israel, you're supposed to go into the Army first, and they have a computer science division, I would have done that. But regardless of how successful Greplin is, say, even if we go public someday, my parents won't be satisfied unless I get a degree. They won't speak to me. But, really, I've been completely focused on the company, and haven't given it too much thought.

Did you always intend to become an entrepreneur?

I was always fascinated by the greater speed start-ups function at versus larger corporations.

It was always something I wanted to do—the unexpected thing was how quickly that happened. I thought I'd go to the Army, develop relationships with intelligent guys, and then three years later maybe start something.

How does your life and work now compare to what you see yourself doing in five years?

It'd be really great for me personally if we were able to keep growing Greplin in the next five years. If we can create something that's a household name and that people use every day, that's a dream.