Tiny stocks don't get a lot of love on Wall Street -- and by tiny I mean companies that have a share price of under $5. According to the Securities and Exchange Commission, any stock that trades at "less than $5 per share" is referred to as a penny stock. Penny stocks are usually highly speculative investments that we long-term investors leave to the traders. Futhermore, many are often listed on over-the-counter exchanges as opposed to reputable exchanges like the NYSE.

However, not every stock that has a share price under $5 deserves to be thrown out with the bathwater. Some of the stock markets' hidden gems can be found with share prices in the low single-digits. After all, great businesses have to start from somewhere.

A growing stack of coins next to a sprouting plant.

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If you're looking for the next Mighty Mouse of sorts, take a closer look at these three top stocks under $5.

Yamana Gold

If you were to just look at the headline figures for Yamana Gold (NYSE:AUY), a gold producer with properties in North and South America, in the first and second quarter of this year, you'd probably turn around and walk away. In fact, Yamana's missed Wall Street's profit per share consensus for five consecutive quarters. But if you were to turn your back on Yamana now, you'd be overlooking what could be one of the most prolific growth stories throughout the remainder of the decade.

Yamana currently has six producing mines, but it's about to get some new additions. Its Cerro Moro mine remains on budget and on schedule with production slated to begin in early 2018. Over its first three years of production, Cerro Moro should yield an annual average of 150,000 ounces of gold and 7.2 million ounces of silver. Similarly, the recommissioning of C1 Santa Luz, which is also expected in 2018, should add an average of 114,000 ounces of gold annually over the approximate 10-year mine life. On a smaller note, the Suruca development within the Chapada mine could be producing by 2019, with a yield of 45,000 ounces of gold to 60,000 ounces of gold annually for up to five years. All of this new production is expected to boost revenue by about 33% and cash flow per share by roughly 50%!

Gold bars laid next to one another.

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Gold investors also shouldn't overlook a number of macroeconomic catalysts that could positively impact Yamana's margin. For instance, even though higher interest rates are generally bad news for spot gold, we're seeing plenty in the way of domestic and international political uncertainty, and the U.S. dollar has been pushing to greater than one-year lows. The dollar and gold usually move in opposite directions. If the price of gold goes up, Yamana's margin would be expected to follow.

Despite its sub-$3 price tag per share, Yamana carries around a very respectable $2.6 billion market cap. This is a small stock in share price only -- it's a top stock in the making within the gold industry.

Geron

If you prefer to live a little more dangerously and enjoy a good risk-versus-reward stock, then clinical-stage biotech Geron (NASDAQ:GERN), with its share price of just $2, could be the shot in the arm you're craving.

The risk with Geron is plainly apparent: It has one drug in development (imetelstat) and has done essentially nothing with its other drug development ventures throughout the years. Like Yamana's recent quarterly results, Geron's history is probably enough to make fundamental-focused investors turn up their nose and walk away. But there's a really intriguing story behind imetelstat that could add significant value to Geron's $325 million market cap.

Something amazing happened roughly four years ago: Geron went from potentially staring down bankruptcy to reporting exceptionally promising early-stage results in an investigator-sponsored study that showed imetelstat led to partial and complete responses in patients with myelofibrosis (a rare type of bone marrow cancer). This was notable in that no previous drug had ever demonstrated a clinical response in treating myelofibrosis. There's currently a Food and Drug Administration-approved therapy on the market named Jakafi that treats the symptoms associated with the disease, but it does nothing to slow or halt disease progression.

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This promise is what lured in Johnson & Johnson (NYSE:JNJ) in late 2014. Johnson & Johnson snagged a licensing partnership with Geron for $35 million in upfront cash and $900 million in possible development, regulatory, and sales milestones for myelofibrosis and myelodysplastic syndrome. While there have been concerns from Wall Street in recent months about the trials being narrowed a bit to specific patients pools, we're still talking about a drug that has game-changing potential for myelofibrosis and myelodysplastic syndrome patients.

If imetelstat proves its worth in later-stage studies, it's not out of the question that J&J considers scooping up Geron in a buyout. For now, more risk-oriented long-term investors need to wait for more clinical data.

Plug Power

A final top stock under $5 that could offer alluring upside over the long run, assuming management gets its act together, is hydrogen fuel cell developer Plug Power (NASDAQ:PLUG).

There are two main reasons why investors have generally shied away from Plug Power and its alternative energy solutions. First, the company just keeps losing money. In fact, it reported a considerably wider-than-expected loss in the second quarter and has missed Wall Street's consensus in 11 of the past 12 quarters.

Secondly, the company has regularly issued common stock in order to fund its operations, which is a fairly common practice for money-losing companies. Between 2012 and the end of Q2 2017, Plug Power's outstanding share count has ballooned from 34 million to 206 million. Unfortunately, long-term shareholders take it on the chin when that happens since their existing shares are diluted as a result.

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However, Plug Power has also shown that it can snag the industry elephants, and that could go a long way to juicing its long-term growth prospects. Between Q1 2015 and Q2 2017, it's more than doubled the number of cumulative GenDrive deployments (e.g., GenDrive forklift fuel cells) to 16,100, and its vertically integrated GenKey sites, which handle everything from the fuel cell systems to infrastructure and support, have nearly quadrupled to 48 in the same period. This expansion can be attributed primarily to its growing relationship with Wal-Mart (NYSE:WMT) and to a smaller, but still very important degree, Amazon.com (NASDAQ:AMZN). Wal-Mart recently signed a deal with Plug Power for 30 new GenKey sites over the next three years, while Amazon and Plug forged a deal in April of this year for multi-site GenKey deployments. But, the caveat with these deals is that Wal-Mart and Amazon both received Plug Power warrants, which could further balloon its outstanding share count, as my colleague Travis Hoium pointed out.

If management can tighten the reins on dilution and focus on building its relationships with Amazon and Wal-Mart, it could become profitable on a recurring basis as soon as 2019. In fact, Wall Streets' consensus calls for $0.19 in full-year EPS by 2020. If Plug can indeed hit that figure, its $2 share price would be a remarkable bargain.

Sean Williams has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Amazon and Johnson & Johnson. The Motley Fool has a disclosure policy.