E-commerce and cloud behemoth Amazon (NASDAQ:AMZN) hit the trillion dollar valuation mark recently. But, it didn’t stick. Amazon stock dropped quickly after it hit $1 trillion, and has since languished at a valuation around $980 billion. But, don’t confuse an inability to the hold a trillion dollar valuation with weakness in Amazon stock.

During any time period you choose in excess of a month, Amazon stock has been anything but weak.

Over the past month, Amazon is up more than 5%. The S&P 500 is up just 2.5%. Year-to-date, Amazon stock is up 70%. The market is up less than 10%. During 2017, Amazon stock rose more than 55%. The market was up 20%. In 2016, a bad year for Amazon, the stock was still up 11%, versus a 10% gain for the S&P 500. In 2015, Amazon stock rose nearly 120%. The market was down that year.

Big picture, Amazon stock hasn’t been weak for a long time. It’s not weak today, and it won’t be weak going forward, either. This company has simply too many growth catalysts to keep the stock weak for an extended period of time.

In 2019, Amazon will have four big growth catalysts. Of course, the ecommerce and cloud businesses will continue to report strong numbers. But, Amazon will also get a big boost from its still nascent digital ads business and forthcoming e-pharmacy business.

Both of those businesses promise to be multi-billion dollar revenue generators one day, and their ramp in 2019 will likely power yet another year of out-performance for Amazon stock.

E-Pharmacy Could Be Huge

Amazon has long looked for a way to enter the pharmacy market. The company finally found its entry point a few months ago when the ecommerce giant acquired e-pharmacy company PillPack for $300 million.

PillPack isn’t that big a company, but importantly, the company has pharmacy licenses in all 50 states. Thus, the acquisition of PillPack allows Amazon to overcome the one big obstacle to starting at e-pharmacy business: acquiring the licenses.

Next up? A massive e-pharmacy business that will look a lot like Amazon’s e-commerce business.

The pharmacy market is a $300 billion market in the United States. Just like with traditional retail, not all of that market will shift online right away. About 30% of all apparel sales happen online now, and that rate has been steadily climbing for years. I realistically think it balances out around 50%. That feels like a good e-commerce penetration rate for pharmacy sales, too.

That puts Amazon’s addressable market in e-pharmacy at $150 billion. Amazon controls about half of the entire U.S. ecommerce market. There is reason to believe Amazon’s share in the e-pharmacy market will be even bigger, considering that more than 70% of consumers would be willing to purchase prescription drugs through Amazon .

Nonetheless, let’s assume 50% market share. That implies revenues of $75 billion for Amazon e-pharmacy. In a long-term window, pharmacy operators tend to be valued at 0.5X to 1X trailing sales.

Amazon’s e-pharmacy business should be valued at the high-end of that range considering its bigger growth prospects. Thus, Amazon’s e-pharmacy business could easily tag on another $75 billion, if not $100 billion or more in market cap over the next several years.

Digital Ads Could Be Bigger

Amazon is one of the most visited websites in the world. The Amazon app is also among one of the most downloaded and widely used apps in the world, especially on the commerce front. Indeed, in terms of digital traffic, Amazon is the realm of Facebook (NASDAQ:FB), Google (NASDAQ:GOOG), YouTube, and Yahoo.

In that group, Amazon is the only one that doesn’t get most of its revenues from digital ads. Instead, Amazon’s digital ad business is operating at an $8 billion run rate. While that my seem big, it is tiny next to Facebook and Google, two companies whose advertising businesses raked in essentially $40 billion and $100 billion, respectively, in revenues last year.

Amazon won’t ever become as big as Facebook and Google. After all, Amazon is one website and one platform. Facebook is four 1-billion user apps. Google is two hugely trafficked websites.

But, Amazon is already starting to steal market share from both Facebook and Google, and there is a realistic chance for Amazon to become a strong third player in this market. According to eMarketer figures and SEC filings, Facebook controlled about 17% of the global digital ad market last year, while Google captured about 40%.

Over the next several years, Amazon could reasonably grow its share to 10% thanks to its wealth of consumer data, 100 million-plus Prime subs, and huge digital traffic flows. That would make it a formidable third player in the digital ad market. At 10% market share in five years, Amazon’s digital ad business could be a $40 billion-plus business by 2022.

Facebook is a $40 billion digital ad business today. It has a market cap of nearly $500 billion. Thus, Amazon’s digital ad business could reasonably be worth $500 billion in five years.

Bottom Line on Amazon Stock

Between e-pharmacy and digital ads, Amazon could add an extra $600 billion to its already huge valuation, and that’s just considering the U.S. side of the e-pharmacy business. If Amazon goes global with that business, then $600 billion will prove to be a conservative estimate.

In totality, there are simply too many huge growth drivers to keep Amazon stock depressed for long. This stock may not have held its trillion dollar valuation. But, don’t confuse that for weakness in the stock.

Long-term, Amazon stock will reclaim the trillion dollar mark, and be on its way to a $1.5 trillion and even $2 trillion valuation.

As of this writing, Luke Lango was long AMZN, FB, and GOOG.