You might find this a bit cheeky, but the hottest stocks on the market aren't stocks at all -- they're exchange-traded funds (ETFs). Small-cap ETFs.

According to a recent article in The Wall Street Journal, small-cap ETFs are fast becoming the latest, greatest way for hedge funds and pension funds to gain exposure to small companies -- one of the best-performing sectors in the market. Indeed, small caps have outperformed larger companies several years in a row now, and they did so again in 2006 by three percentage points.

That's incredible performance that a lot of new money is chasing.

Where the big money flows
To wit, the iShares Russell 2000 Index, which counts smallish companies such as $2.7 billion JetBlue Airways (NASDAQ:JBLU), $2.6 billion Hologic (NASDAQ:HOLX), and $2.2 billion Westar Energy (NYSE:WR) among its top holdings, has seen its assets increase from $7 billion to more than $12 billion since the end of 2005.

Even more incredibly, the Vanguard Small Cap ETF -- which tracks the MSCI US Small Cap 1750 Index and invests in the likes of $4 billion FMC Technologies (NYSE:FTI), $4.1 billion Range Resources (NYSE:RRC), and $3.8 billion Nasdaq Stock Market (NASDAQ:NDAQ) -- has seen its assets more than double over the past 12 months.

Now, you'll notice an oddity here: The top holdings of these ETFs aren't really small caps at all -- they're all capitalized at $2 billion or more. The more practical definition of a small cap is a company capitalized at less than $2 billion, and that's the soft cap we use to make recommendations at our Motley Fool Hidden Gems small-cap newsletter.

Stocks vs. sectors
The other oddity is that very smart hedge and pension fund managers are handing their money over to passive indices. They're not making bets on specific companies at all, but rather on the entire small-cap sector. That's an interesting move, since broad indices tend to be more efficiently priced than individual companies -- there are thousands of data points to evaluate rather than just a few -- and their returns will always be muted because the laggards will weigh down the best performers. The mind-blowing returns will only come when one invests in the very best companies at the very best prices.

So why aren't hedge and pension funds making bets on individual stocks? Well, frankly, because they have too much money.

The downside of riches
You're probably thinking that's a pretty good problem to have, but it really isn't. Remember, Warren Buffett has said that he could earn 50% annual returns if and only if he had less than $1 million to invest. That's because he could then move nimbly in and out of small stocks -- the stocks with the best returns -- without moving the price or attracting a lot of attention. See, the problem with small companies is that their shares don't trade very much, and they're not very liquid. That's a problem for professional investors, but it's an incredible opportunity for individual investors like you and me. For us, small caps are the very best place to make money.

Once more, from the top
So what are the takeaways here?

  1. Small caps are a very profitable sector.
  2. Professional money managers are flocking to the sector to make money.
  3. Unlike professional money managers, you have the ability to put your money behind the very best small companies and (you hope) earn the best returns.

If you'd like to start investing in small caps and want a little help doing so, come join us at Motley Fool Hidden Gems. Our team -- led by Motley Fool co-founder Tom Gardner and senior analyst Bill Mann -- specializes in finding and recommending the best small public companies. We're having some success at it: Our recommendations have returned more than 47% on average over the past two-plus years, vs. just 21% for the large-cap-laden S&P 500 index.

Nearly every smart investor is striving to have superior small-cap exposure. Be our guest at Hidden Gems free for 30 days, and we can help you achieve just that.

This article was originally published on April 21, 2006. It has been updated.

Tim Hanson does not own shares of any company mentioned in this article. JetBlue is a Motley Fool Stock Advisor recommendation. No Fool is too cool for disclosure.