Who needs amusement parks and roller coasters when you have the stock market, right? This year, the broad-based S&P 500 collapsed by 34% in roughly one month and soared back to all-time highs in under five months.

This volatility has cued long-term investors to put their money to work in innovative brand-name businesses. But these wild vacillations in equities have also attracted quite a few young and novice investors.

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Online investing platform Robinhood, which is best known for its commission-free trades, fractional-share investing, and gifts of free stock to new members, has been particularly adept at signing up millennial and novice investors. This year, the platform has added millions of new account holders, with the average age of its members being just 31.

On the one hand, it's fantastic news that younger investors are putting their money to work in the greatest wealth creator on the planet. After all, time is the ally of millennial investors: The earlier they start, the more compounding can work in their favor.

On the other hand, Robinhood isn't exactly setting up its members for success. Although it's giving them a platform to make commission-free trades, it's not offering the educational tools needed for investing success. As a result, most Robinhood investors tend to chase growth stocks over the very short term and occasionally end up holding duds.

However, there's a compromise to be made on this front. Chasing high-growth stocks is actually a really smart strategy for millennial investors with time on their side. If Robinhood investors intend to hold their purchases for years, rather than days or weeks, the following three high-growth stocks make for excellent buys.

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Palantir Technologies

I'm excited to report that data mining company Palantir Technologies (PLTR 0.56%), which recently went public via a direct listing, has already found its way onto Robinhood's leaderboard -- i.e., the platform's 100 most-held stocks. Investors who hang on to Palantir for the years to come should be handsomely rewarded.

One key advantage for investors is Palantir's choice to avoid the traditional initial public offering route. Not having its valuation pumped up by a traditional investment bank prior to its debut has allowed Palantir to trade at roughly 20 times this year's projected sales. That's not exactly inexpensive for a tech stock, but it's substantially lower than the high double-digit and even triple-digit sales multiples we've witnessed from recent cloud IPOs. In other words, Robinhood investors can scoop up Palantir at a reasonable price.

Unlike most companies right now, Palantir is also seeing its sales growth accelerate. An uptick in demand on its Gotham platform, which provides data mining services to the federal government, along with the organic and inorganic growth potential of its Foundry platform for enterprise clients, offers Palantir double-digit growth potential for years to come. Keep in mind that Palantir only has 125 clients at the moment, so it's still just scratching the surface with its Foundry platform

At 12 times Wall Street's estimated full-year sales in 2022, Palantir is a high-growth stock for millennial investors to own.

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Teladoc Health

Telemedicine giant Teladoc Health (TDOC -2.91%) is a transformational company that'll probably be on the leading edge of innovation in the healthcare space for many years to come.

There's no question that Teladoc has benefited from the coronavirus disease 2019 (COVID-19) pandemic. With physicians wanting to keep at-risk and potentially infected patients out of their offices, virtual visits have soared. During the June-ended quarter, Teladoc registered a 203% increase in year-over-year total visits.

But this isn't just a pandemic play. The company's compound annual growth rate between 2013 and 2019 was 74%. Furthermore, telemedicine is a win for the entire healthcare sector. Physicians and patients gain convenience, while insurers face lower billing fees tied to virtual visits.

Teladoc Health is also in the process of acquiring applied health signals company Livongo Health (LVGO) in an $18.5 billion cash-and-stock deal. Livongo's solutions help chronically ill patients lead healthier lives. Recently, Livongo unveiled that it leveraged Teladoc's existing partnership with Florida Blue, a subsidiary of Guidewell, to provide its services (without patient copay) to approximately 50,000 Florida Blue diabetes members. This combination will be a high-growth match made in heaven. 

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Image source: Facebook.

Facebook

Buying into high-growth companies they're familiar with keeps millennials excited about their investments. That's why social media platform Facebook (META -10.56%) is worth consideration.

Don't let Facebook's nearly $790 billion valuation fool you. This isn't some stodgy old company ready to be put out to pasture. It's still a high-growth powerhouse with significant upside.

Think about this for a moment: Facebook owns four of the six most visited social sites on the planet -- Facebook, WhatsApp, Instagram, and Facebook Messenger. It's only monetizing Facebook and Instagram at the moment. When the company does open the floodgates on WhatsApp, which has roughly 2 billion users, and Facebook Messenger, it's going to receive an insane growth boost. 

Another factor to consider is Facebook's monthly active user (MAU) count. This is a company that ended June with 2.7 billion MAUs on Facebook and over 3.1 billion MAUs if you count its other platforms. Advertisers understand that there are no other platforms where they can access so many targeted users at once. Facebook's ad-pricing power is unrivaled in the social media space, and that's great news for its shareholders.