Craig Silverstein, the first employee Google co-founders Larry Page and Sergey Brin hired, has just now leaving the company to join Khan Academy.

Khan Academy is a nonprofit education organization, which provides freely available online resources for teachers, students and others looking to expand their education. It has an extensive video library, with content for grades K-12 in math, biology, chemistry, physics, history, finance, etc.

At Google, Silverstein created some of the company’s original IT components, which were critical in supporting the search engine’s growth. As you can see from some of the talks he’s given, he’s been involved with some of Google’s more educational endeavors:

Kara Swisher shares a statement from a Google spokesperson on Silverstein’s departure: “Craig’s been with Google since the early days. He was instrumental in the development of search and made numerous contributions to Google over the years. We wish him all the best at the Khan Academy and know that he will do great things to help them promote education around the world.”

She also shares his goodbye email to the company. In that, Silverstein says:

Some of you thought this day would never come (as one person once put it: “Will you die at Google?”), and it was an extremely difficult choice. I am as passionate about Google’s mission now as I’ve ever been, and as proud of the work we’re doing to achieve it. While a lot has changed at Google over the years, I think we’ve done a remarkable job of staying true to our core mission of making the world a better place by making information more accessible and useful. I am looking forward to pursuing that same mission, though in a slightly different way, at Khan.

I’m extremely grateful to have had the opportunity to work with such smart, passionate, and interesting people — not just a few, either, but (almost 🙂 ) everyone I worked with. I’m grateful not just that I had so many co-workers I could respect, but even more that I had so many that I could count as friends. I will miss that most of all, and I hope you will continue to be in touch. I also accept lunch invitations!