Microsoft Corp co-founder Bill Gates, who made the company one of the world’s most valuable technology firms, stepped down from the board on Friday to focus on philanthropic works related to global health, education and climate change. The billionaire and his wife Melinda run one of the world’s largest charities, the Gates Foundation, which has billions in assets and funds global health programmes to combat disease and poverty.

Gates, 64, has been scaling back his involvement in the Redmond, Washington-based company for more than a decade. Most recently he’d been serving as an adviser to current Chief Executive Officer Satya Nadella on technology areas including productivity, health software and artificial intelligence, and he will continue to do so.“Microsoft will always be an important part of my life’s work and I will continue to be engaged with Satya and the technical leadership to help shape the vision and achieve the company’s ambitious goals," Gates wrote in a blog post . “I feel more optimistic than ever about the progress the company is making and how it can continue to benefit the world."

Gates quit his full-time executive role at Microsoft in 2008 and remained as chairman of the board till 2014. Since then he has been a board member.

“It’s been a tremendous honor and privilege to have worked with and learned from Bill over the years,” Chief Executive Officer Satya Nadella said.

With the departure of Gates from Microsoft Board, it will now consist of 12 members, the company said.

Under Gates’s leadership, Microsoft grew from a provider of the basic software code used to run business and home machines in the early years of personal computers into the dominant provider of software in computing from workplace productivity to internet and gaming. Under Gates’s successor, Steve Ballmer, Microsoft’s position in the tech industry was challenged by competitors like Google and a resurgent Apple Inc.

Gates will also exit the board of Berkshire Hathaway Inc., the company run by his longtime friend Warren Buffett. As part of the shuffle, Kenneth Chenault, former CEO of American Express Co., will join Berkshire’s board, Buffett’s company said Friday in a regulatory filing.

“He leaves an enduring legacy of curiosity and insight that serves as an inspiration for us all," Microsoft Chairman John Thompson said in the company statement.