Americans across generations have gotten the message: Investing is a great way to pave the way to wealth and financial freedom. That's probably why more than half of Americans today own stock, and though baby boomers own the largest share, according to data compiled by The Motley Fool, younger folks also have piled into this wealth-building opportunity.

In fact, millennials own about $4.4 trillion in stocks, and these investors tend to favor U.S. stocks and growth stocks. Considering the S&P 500 has been roaring higher over the past two years and through this year, led by these sorts of equities, millennials may be reaping the rewards of this choice. Of course, when investing, it's important to hold on for the long term rather than selling quickly for a short-term gain. This is with the idea that you've chosen quality players that have what it takes to excel over time.

And with this in mind, let's check out three U.S. growth stocks that are perfect for millennials to add to their portfolios right now and hang onto for the long term.

A group of young investors looks at something on a computer.

Image source: Getty Images.

CoreWeave

CoreWeave (CRWV 2.77%) stock has soared more than 200% since its March initial public offering, but this player may have much farther to go. The company has brought to market the right service at exactly the right time: high-power compute capacity for artificial intelligence (AI) workloads. CoreWeave offers its pool of more than 250,000 graphics processing units (GPUs) for rent to AI customers -- and demand and revenue have exploded higher.

In the most recent quarter, CoreWeave's revenue tripled to more than $1.2 billion, and that's after a 420% gain in the previous quarter year over year. Considering forecasts for AI infrastructure spending of as much as $4 trillion by the end of the decade, momentum may continue. It's also important to note that later on in the AI story, as AI models are put to work on real world problems, they will continue to require this compute power -- this suggests CoreWeave may have a very long growth story ahead of it.

Another plus? AI chip giant Nvidia is a believer in CoreWeave's strengths as it owns 7% of the stock.

Chewy

If you have a pet, you may recognize the name Chewy (CHWY -0.81%). This online retailer sells everything you might want as a pet parent, from pet food and treats to toys and even prescription medicines. The company has proven its financial strengths in recent years as it's become profitable, increased revenue, and is debt-free.

On top of this, it's taken steps that should boost growth over time, from expanding its e-commerce presence into Canada to opening veterinary clinics in the U.S. These clinics are a fantastic way to add another revenue stream -- and introduce new customers to Chewy's e-commerce offerings, considering some pet owners may not routinely shop online for their pets.

What I like in particular about Chewy is that it's built a strong customer base as we can see through its AutoShip business, a service that automatically reorders your favorite products and ships them to you. AutoShip makes up more than 80% of Chewy's total sales, and this offers investors great visibility on sales from quarter to quarter.

An Amazon driver delivers a package.

Image source: Amazon.

Amazon

Amazon (AMZN -0.95%) operates in two areas that are well positioned to offer investors growth in the coming years: e-commerce, through Amazon.com, and cloud computing, through Amazon Web Services (AWS). These businesses are leaders in both of these markets, and this has generated billions of dollars in earnings over the years.

And now, Amazon.com and AWS are benefiting and set to benefit in the coming years from AI. The company uses AI to streamline its fulfillment network operations and much more, saving time and money -- AI also may guide customers to the right products as they shop, and AI helps select the best delivery routes, shortening delivery times.

Amazon also sells AI tools and services through AWS, and this represents a huge opportunity for revenue growth. It's already helped AWS reach a $123 billion annual revenue run rate.

Meanwhile, steps Amazon took a few years ago to revamp its cost structure should help it optimize profitability over the long term -- this along with its position in e-commerce and cloud and prospects in AI make it a fantastic growth stock to snap up now and hold.