For investors leery of individual stocks, exchange-traded funds (ETFs) can provide an excellent alternative. These funds trade just like stocks but track groups of stocks or commodities, giving access to a broader investment vehicle than an individual stock.

Buying an ETF is a great way to gain exposure to specific regions, such as emerging markets, or sectors, such as oil, solar, or airlines, for example. Investors interested in just getting a piece of the market can buy a few shares of an index fund such as the SPDR S&P 500 ETF (SPY) or the iShares Core S&P 500 ETF (IVV), which track the S&P 500, while risk-seeking investors might prefer more volatile ETF's. 

Following, three of our contributors share their pick for the best growth ETF today. 

Andres Cardenal: Emerging markets aren't particularly popular among investors right now. Economic jitters in countries such as China and Brazil, in combination with slumping commodities prices, are scaring investors away from these markets. On the other hand, there are strong reasons to consider adding some long-term exposure to emerging markets as part of a globally diversified portfolio, and WisdomTree Emerging Markets Small Cap Dividend Fund (NYSEMKT:DGS) is a smart vehicle to invest in those intriguing corners of the world

As opposed to other emerging-markets ETFs, which are typically focused on large-capitalization companies and commodity producers, the ETF holds a basket of nearly 700 dividend-paying small-capitalization companies in emerging markets. WisdomTree Emerging Markets Small-Cap Dividend Fund is heavily weighted toward sectors such as financials, technology, and consumer discretionary, so it offers substantial potential to profit from the rise of the middle class in emerging markets over the decades to come.

Importantly, WisdomTree Emerging Markets Small-Cap Dividend Fund weights different companies in accordance to their dividends, not their market capitalization. Dividend payers are generally solid businesses generating consistent cash flows, and this is a big plus when investing in emerging markets.

At current prices, WisdomTree Emerging Markets Small-Cap Dividend Fund pays a dividend yield around 3.3%, and the annual expense ratio is at a reasonable 0.63%.

Joe Tenebruso: Climate change is arguably one of the greatest threats to human existence. Fortunately, there are some innovative companies working to help society meet this monumental challenge. In fact, the entire solar-power industry is built on the premise that energy harnessed from the sun can be far cleaner -- and is more abundant -- than that derived from fossil fuels. And thanks to recent advances in technology, solar power is also rapidly becoming a less expensive source of energy in many parts of the world.

"On rooftops from Arizona to New York, solar is saving Americans tens of millions of dollars a year on their energy bills." —@POTUS #SOTU

— The White House (@WhiteHouse) January 13, 2016

While the long-term market opportunity for solar power is clearly massive, the challenge -- as is typically the case when investing in disruptive technologies -- lies in the difficulty of identifying the winners, since the dynamic nature of the solar industry can result in only fleeting periods of competitive advantage.

As such, often the best way to invest in emerging industries is through a sector fund. In this way, investors are able to profit from the growth of the overall industry without having to choose between the winners and losers. In this regard, those seeking to invest in the high-growth solar industry may wish to consider Guggenheim Solar ETF (NYSEMKT:TAN). TAN tracks an index of approximately 25 solar energy companies that are selected based on the relative importance of solar power to the company's business model.    

Industry leaders SolarCity and First Solar are the ETF's two largest holdings, representing roughly 6.8% and 6.7% of the overall portfolio, respectively, so investors in TAN will gain significant exposure to the companies that are currently winning in this fast-growing field. And by also spreading their bets among more than 20 other leading solar companies, TAN owners can increase their chance of profiting from the huge growth opportunity that is solar energy.

Jeremy Bowman: The first days of 2016 have rattled the markets like almost nothing else since the recession. A crash in oil prices and a rampant sell-off in China have sent major U.S. indexes spiraling downward into correction territory. But long-term investors know that no market condition lasts forever. Markets will calm down and stocks will eventually bounce back. It's just a matter of time.

That's why I'm recommending VelocityShares Daily Inverse VIX ST ETN (NASDAQ:XIV), an ETF tied to the CBOE volatility index or VIX. Also known as the "fear factor," the VIX spikes in market crashes such as this one. XIV moves inversely to the VIX, so as the VIX has climbed, XIV has tumbled. As of this writing, XIV is trading below $18, its lowest level since 2012. Before the August crash, it was above $50. 

The VIX itself is a volatile ticker often moving in double-digit percentage swings, and the XIV is volatile as well on a day-to-day basis. But the VIX is abnormally high right now, trading above 29, compared with its median closing point over a recent 10-year period of 17. No one knows where the market is going in the short term, but we do know that volatility is a temporary condition. Mean reversion is one of the strongest laws in finance, and the VIX will eventually revert to its mean. When that happens, XIV will soar.

XIV is not a ticker to hold long-term because of its volatility, but a recovery to $30 within the next few months would not be an unreasonable expectation.

Andrés Cardenal has no position in any stocks mentioned. Jeremy Bowman owns shares of VelocityShares Daily Inverse VIX Short Term ETN. Joe Tenebruso has no position in any stocks mentioned. The Motley Fool owns shares of and recommends SolarCity. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.