Bill Gates is paying tribute his late friend, Paul Allen, who co-founded Microsoft with him in 1975.

Allen passed away at the age of 65 on Monday from complications from non-Hodgkin’s lymphoma, a cancer that kills nearly 20,000 people a year. At the time of his death, Allen was listed by Forbes as the 44th richest person in the world with a net worth of $20.3 billion.

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In an article published to the Wall Street Journal on Thursday, Gates, 62, reflected on when he first met Allen in grade school, and how their friendship would go on to reshape the world through technology.

“I met Paul Allen when I was in 7th grade, and it changed my life, Gates wrote in the Journal. “I looked up to him right away. He was two years ahead of me in school, really tall, and proved to be a genius with computers… Eventually, we were spending just about all our free time messing around with any machine we could get our hands on.”

The two would often sneak off during late hours to use the computers at the University of Washington, something Gates said he wouldn’t have had the nerve to do without Allen by his side.

Back then, Allen was able to foresee how powerful and essential computers would one day become. When Allen came across an issue of Popular Electronics that featured a powerful computer that was going to be released, he convinced Gates to join him in placing all of their focus into getting in on the computer industry before it took off without them.

Image zoom Paul Allen in 2008 Larry Busacca/WireImage

“That moment marked the end of my college career and the beginning of our new company, Microsoft,” Gates recalled, adding that Allen’s talents largely helped to make Microsoft successful at its inception. “As the first person I ever partnered with, Paul set a standard that few other people could meet. He had a wide-ranging mind and a special talent for explaining complicated subjects in a simple way.”

Allen was diagnosed with Hodgkin’s lymphoma in 1982, which lead him to step down from his role at Microsoft the following year. The cancer would go into remission until 2009, when he was diagnosed with non-Hodgkin’s lymphoma. After beating this second bout of cancer, be rediagnosed with it this year.

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Thanks to his philanthropic efforts to help low-income communities, Allen became a beloved figure in the Pacific Northwest, where he also owned two sports franchises — the Portland Trailblazers and his hometown Seattle Seahawks. Allen had a wide array of interests and wanted to share them with others, Gates said, which led him to found museums, including the Flying Heritage & Combat Armor Museum and the Museum of Pop Culture.

Image zoom Bill Gates Chesnot/Getty

“Paul was cooler than I was. He was really into Jimi Hendrix, and I remember him playing ‘Are You Experienced?’ for me,” Gates wrote in the Journal. “I wasn’t experienced at much of anything back then, and Paul wanted to share this amazing music with me. That’s the kind of person he was. He loved life and the people around him, and it showed.”

Gates — who is currently in Brussels this week to create a pilot fund to invest millions of dollars into European companies working to stop climate change — said he will remember all of the good things that Allen did for the world in the years since they helped to revolutionize personal computing.