Apple announced a significant leadership change yesterday, revealing that John Ternus will take over as CEO from Tim Cook later this year.

Following this announcement, technology leaders (and others) took to social media to congratulate Cook.

Here is the message from Google CEO Sundar Pichai on social media:

Congratulations @tim_cook on a great run, I have always appreciated your deep commitment to Apple’s mission and wish you all the best in your new role! I look forward to working with John!

And here is the message from OpenAI CEO and co-founder Sam Altman:

Tim Cook is a legend.

I am very grateful for what he has done and very grateful for Apple.

Warren Buffett, who retired from Berkshire Hathaway this year, said to CNBC:

If it weren’t for Tim Cook, Apple wouldn’t be the Apple it is today. What he has done for Apple is something that no one I know could have done.

To encompass the world and get along well with countries of all backgrounds, to treat customers, the people who work for him, and certainly shareholders right, of which we are lucky to be one… he is truly one of a kind.

Qualcomm CEO Cristiano Amon:

Congratulations to @tim_cook for over 15 years of leadership and to CEO John Ternus.

The Governor of Alabama, Kay Ivey, Cook's home state:

In Alabama, we will always be proud of Tim Cook! He is an Alabamian born in Mobile and a graduate of Auburn University. I wish @tim_cook continued success and I am grateful for what he has done and will continue to do for our state.

President Donald Trump (direct quote from his website):

I am a big fan of Tim Cook, just as I am of Steve Jobs, but if Steve had not been taken from this planet so young and had run the company instead of Tim, the company would have done well, but it would not have been as good as it is under Tim. For me, this started with a phone call at the beginning of my first term. He had a very big problem that only I, as President, could solve. Most people would have paid millions of dollars to a consultant they probably didn’t know, but he would have said he knew me well. The fees would be paid but the work wouldn’t get done. When I picked up the phone, wow, Tim is calling Apple (Cook!), how big is that? I was very impressed that the head of Apple was calling me. Fortunately, he explained the problem, it was a tough situation, I thought he was right, and I handled it quickly and effectively. This was the beginning of a long and very beautiful relationship. During my five years as President, Tim would call me, but never too much, and I would help him as much as I could. Years later, after 3 or 4 BIG HELP moments, I started telling people, everyone who was listening, that this guy is a great executive and leader. He makes these calls to me, I help him (but not always, because sometimes he can be very aggressive in his requests!), and he gets the job done QUICKLY without spending a dime on those very expensive (millions of dollars!) consultants who sometimes do their jobs and sometimes don’t. Anyway, Tim Cook had a FANTASTIC career, almost unmatched, and will continue to do great things for Apple. In short, Tim Cook is an incredible man!!! President DONALD J. TRUMP