One of the most confounding parts of investing in stocks is the volatility. Many investors shy away from making individual picks out of fear their investment will crater. However, that volatility is also one of the best reasons to invest in individual stocks. Whether it's from consistently strong business growth or a rebound from overly pessimistic pricing, owning individual businesses can help fuel big returns.

With the goal of building a diversified list of big winners that have more possible upside ahead, three stocks worth a look are Paycom Software (NYSE:PAYC), Universal Display (NASDAQ:OLED), and The Trade Desk (NASDAQ:TTD). All three have doubled in the last year, but just because a stock has skyrocketed doesn't mean you've missed your chance to go along for the ride.

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Helping drive digital transformation

Paycom Software operates a cloud-based suite of tools to help businesses manage all of their human resource needs. As digital transformation -- a catch-all phrase used to describe an organization's digital upgrades -- sweeps across the globe, Paycom is filling an important niche in helping with everything from employee recruitment and hiring to benefits and retirement planning. As a result, shares are just shy of a 100% year-over-year increase as of this writing.

The proof, of course, is in the numbers. Revenues through the first three quarters of 2019 are up 31% to $544 million, and adjusted EBITDA (earnings before interest, tax, depreciation, and amortization, Paycom's preferred way of measuring the bottom line) is also up 31%. The company is only just beginning to realize a profitable payoff after years of fast sales expansion.

There's still plenty of room for the top line to grow, though. Management once again upgraded its full-year 2019 guidance after the Q3 report, now calling for $733 million to $735 million in sales (previously $728 to $730 million). Adjusted EBITDA also got an upgrade to $311 million to $313 million (previously $306 to $308 million). The figures represent a 30% and 29% increase, respectively, in revenue and EBITDA over 2018.

Of course, Paycom isn't cheap. Shares are currently going for 56 times expected one-year forward earnings. That kind of valuation has several years' worth of double-digit growth baked in. Nevertheless, while I don't think investors should pile into the stock at this point, it's at least worth keeping an eye on with the aim of making a small initial purchase.

A better viewing experience is on the way

OLED screens really got rolling in premium smartphones and wearables a few years ago, and the super-crisp and vibrant ultra-high-definition big screen OLED TV sets hanging on the walls of retailers this Black Friday are still too expensive to be considered the mainstream. That is quickly changing though. Universal Display, which controls many patents and sells materials for the production of OLED screens, is helping get new manufacturing lines up and running, which is lowering the cost for end consumers.

In fact, the company's management team said it expects total manufacturing capacity to grow 50% between the end of 2019 and the end of 2021. That's the same rate of growth that the industry just notched over the last two-year stretch. It wasn't a straight diagonal line to get to this point (OLED production, as with all manufacturing, is cyclical and can be a wild up-and-down ride), but the payoff has been huge for investors. Rebounding from a down year in 2018, Universal shares are up 120% over the last 12 months as of this writing.

Driving those returns is a 71% increase in revenue through the first nine months of 2019, and earnings per share are up a whopping 184%. Universal trades for 50 times earnings per share based on one-year forward expected results. It's another stock trading for a hefty premium, but given that the bottom line is growing faster than sales are, it isn't a totally unreasonable asking price.

Besides, there's a good chance the company's forecast for the next two years will come true. OLED has significant advantages over current incumbent-technology LED: It has greater screen clarity and displays smoother moving images, it's more power efficient, and it's much lighter weight. As costs continue to fall and OLED adoption increases, Universal Display should be a big beneficiary.

Disrupting the global digital advertising behemoth

Spending on global advertising is expected to top $1 trillion within the next decade, and the dollars dedicated to the digital variety are now half of that amount and gaining. Most of the digital money gets spent with Alphabet's (NASDAQ:GOOGL) (NASDAQ:GOOG) Google and Facebook (NASDAQ:FB), but some firms are beginning to make some inroads against the duopoly. One of them is The Trade Desk.

The Trade Desk operates a platform from which advertisers and their agencies can bid on ad slots, as well as build and launch ad campaigns. Known as programmatic advertising, the segment is one of the fastest-growing areas of the business, clocking a 20% pace this year. The Trade Desk is gobbling up market share, too. Through the first three quarters of 2019, revenues are up 40% and adjusted earnings per share up 37%.

The company is investing heavily to maintain its growth trajectory as several secular changes have taken place in recent years. First, a majority of consumer entertainment -- including audio and TV -- has turned to internet-based delivery. The advertising dollars have been slow to catch up, but the catch-up phase has nevertheless begun. With new streaming TV services coming online, those traditional TV ads are beginning to get converted to digital ones. Same goes for streaming audio.

The second is that programmatic advertising is outpacing the average industry growth rate. Advertisers are making the switch because of the higher level of information they have about the consumers they are publicizing to through programmatic ads, meaning a more relevant experience for the audience and a more efficient investment for sellers. That trend is likely to continue in the years ahead, making The Trade Desk one of the best stocks around to take advantage of the global internet-based ad industry even though it trades for a sky-high 63 times one-year forward earnings after doubling in value in 2019.