After beating Wall Street expectations for the fourth quarter of 2015, Google umbrella company Alphabet usurped Apple as the most valuable company in the world on Monday in after hours trading.

For the fourth quarter, Alphabet raked in $21.3 billion in total sales and adjusted profits of $8.67 for every Class A share, the company said in a prepared statement. Total sales were up 18 year over year, while advertising revenue was up 17 percent for the same period.

Shares popped after Alphabet's announcement, rising 1.22 percent to hit $752 per share in normal trading with a market capitalization of $517.17 billion. The stock kept rising after the bell, at one point touching $813 per share, bringing its market cap up to $559.13 billion. Apple ended the day down at $96.43 with a market cap of $538.7 billion.

Alphabet is seeing a renaissance in growth as its advertising business made big gains this quarter. The company's services division also saw wider adoption including Gmail, which passed one billion users in quarter four. Under the Alphabet umbrella, Google's "moonshot" projects" — Wi-Fi balloons, self-driving cars, glucose-reading contact lenses, human longevity — saw advancements, but cost the firm more than $3.56 billion over the last three months of 2015.

Apple, meanwhile, is losing ground after sitting as the world's most valuable company for more than three years. The iPhone maker reached the position in 2011 and throughout most of 2012 before being unseated by Exxon in 2013. Apple retook the lead later that year.

Despite bringing in revenue of $75.9 billion in a record-breaking first quarter, Apple stock is shedding value amid iPhone growth concerns and quickly diminishing iPad sales. For the current quarter, Apple expects year-over-year iPhone unit sales to decline for the first time since the handset launched in 2007.