Arianna Huffington, the editor in chief of The Huffington Post, announced on Thursday she's leaving the pioneering online news company she co-founded.

Thrive Global, a health and wellness startup, will offer "educational workshops, e-courses and certifications to help companies improve the well-being of their employees," according to an internal Huffington Post memo reported in June by CNBC.

In Huffington's absence, an interim editorial committee comprised of Executive Editor Liz Heron, D.C. Bureau Chief Ryan Grim and News Director Katie Nelson will lead the search for a replacement:

Huffington's departure was spurred by the realization that she couldn't build a new company and run a news organization, she told The Wall Street Journal:

“I really thought I could do both, but as we started building it up, I realized that it really needed my full attention,” she said in an interview. “It is important to know when one door closes and another opens and I felt that moment had arrived.”

The Huffington Post was founded in 2005 by Huffington, Jonah Peretti, Andrew Breitbart and Ken Lerer.

In a farewell memo to the staff of The Huffington Post, Huffington suggested she'll remain a part of HuffPost in spirit, if not in title:

You have made the last 11 years truly unforgettable, and you will always be part of my life. And of course, I’ll never stop recruiting bloggers for Bryan, suggesting splashes to Whitney, and acting as HuffPost’s unofficial Sleep Ombudsman.

HuffPost will have an 11 a.m. meeting to discuss Huffington's departure in more detail, according to the memo.

Here's the memo:

HuffPosters,

For the past 11 years, The Huffington Post has been at the center of my life, and frankly I thought it would be my last act. What we have built together has exceeded my wildest expectations. Never did I imagine when there were just five of us working out of my home office in L.A. that we’d grow HuffPost to be one of the most-visited news sites in the world with editions in (soon-to-be) 16 countries and a Pulitzer Prize-winning global leader in news and politics, solutions journalism and wellness.

As all of you know, since publishing Thrive, I’ve become more and more passionate – okay, obsessed – with burnout and stress and how we can reduce their impact on our lives. As I went around the world speaking about Thrive and hearing people’s stories, I became an even bigger believer in the urgent need to turn that passion into something real and tangible. That’s why, when I signed a new contract last spring, we included a carve-out so that I was able to also launch a venture dedicated to putting Thrive’s values into practice, helping individuals and companies around the world reduce stress and burnout and improve their health and productivity.

When I wrote to you in June, I fully expected to be able to continue leading HuffPost while also building Thrive Global. But it became clear that this was an illusion as Thrive went from an idea to a reality, with investors, staff and offices. One of the Thrive principles is knowing when it's time for a new chapter to begin, and for me that time has arrived. And so I’ve decided to step down as HuffPost’s editor-in-chief. This has been a very difficult decision, but in many ways an inevitable one, given my commitment to building Thrive into a company that has a global impact on how we work and live. Building something from scratch doesn’t become easier or less challenging just because you’ve done it before. There is only one way to do it: with your full attention and all your heart. This is also the only way I have ever known how to run HuffPost through the years, as we have evolved and grown, taking the risks that have led us where we are today.

What made the decision easier is my complete confidence in what we have built together. We have a first-class newsroom, guided by HuffPost’s strongest leadership team ever, starting with Jared who’s been our amazing CEO and partner to me, and Tim who has loved and believed in HuffPost from day one. The talent, commitment and values you all bring to everything you do here make HuffPost what it is – and what you do is now more important than ever. So most of all, I want to end by thanking all of you. I’m filled with gratitude and admiration for all the colleagues and friends that I’ve made over the years on this incredible adventure. You have made the last 11 years truly unforgettable, and you will always be part of my life. And of course, I’ll never stop recruiting bloggers for Bryan, suggesting splashes to Whitney, and acting as HuffPost’s unofficial Sleep Ombudsman.

We’ll gather at 11am ET to discuss in more detail and answer your questions.