Legendary investor Warren Buffett announced some very surprising news on CNBC on Thursday -- that in the first quarter of 2018, Berkshire Hathaway purchased 75 million shares of Apple, putting Berkshire Hathaway's total Apple holdings at a little over 240 million shares.

This purchase is Berkshire's largest buy of Apple shares to date, and now makes the firm the third largest holder of Apple stock after Vanguard and BlackRock.

How notable is this move? For one thing, Buffett is known to not invest in technology companies, citing his lack of understanding them as a reason for not feeling comfortable in investing. However, Buffett revealed at Berkshire Hathaway's annual shareholder's meeting on Saturday that he "blew it" when he passed up early opportunities to invest in Google and Amazon.

He's not going to make that mistake again.

Apple is now 21 percent of Berkshire Hathaway's portfolio, and Berkshire Hathaway owns just below 5 percent of Apple's shares.

Most of all, Buffett's disclosure of this purchase drove up Apple's share price to a record close of $183.83 on Friday, propelling them up 4 percent, or $7. This last week, Apple's stock even increased $21.51 (13.3 percent), adding more than $100 billion to its market cap.

Naturally, Apple CEO Tim Cook says the company is "thrilled" to have Buffett and Berkshire on board as a major investor. "On a personal level, I've always greatly admired Warren and have always been grateful for his insight and advice," Cook says.

As a general rule, it's a good idea to watch what billionaire Warren Buffett does. But if you have been paying attention this week, you now may be looking at your iPhone in a whole new light.