Apple's market cap -- a measure of the value of a company -- is now below $400 billion.
The company passed the milestone as Apple's shares fell 2 percent in trading this morning and the decline continued through the day to a closing price of $420.05, a drop of 2.4 percent from Friday's closing price. At that share price, Apple's market cap is now $394.45 billion. The company's valuation hasn't been that low since late 2011.
Apple's share price has been on a steady decline over the last several months. In the last six months alone, the price has gone down more than 37 percent. Its 52-week high of $705.07 seems like a distant memory at this point.
At a shareholder meeting last week, Apple CEO Tim Cook responded to a question about his company's slumping stock price, saying he doesn't "like it either." He didn't say, however, what he might do to turn things around.
Whether it's really cause for concern, though, is up for debate. In an interview with CNBC's Squawk Box this morning, famed investor Warren Buffett said that CEOs "can't run a business to push the stock price up on a daily basis," adding that his own company, Berkshire Hathaway, "has gone down 50 percent four times in its history."
"When that happens, if you've got money you buy it," he said. And, well, Apple does have $137 billion in its cash reserve, a fact that helped propel the Greenlight Capital insurgency that just came to an end after several contentious weeks.
Buffett is not an Apple shareholder.
Update 1:42 p.m. PT: Updated with the closing price for Apple's shares and the company's market capitalization at that price.