There was a song we Girl Scouts used to sing as we swayed in sisterly harmony around the campfire. It went like this: "Make new friends, but keep the old/ One is silver and the other gold." I know. Corny. But as I read through the names and company descriptions on this year's Inc. 500, that sentimental lyric kept running through my head.

Here's why: I recognized a good number of companies from Inc. 500s past. Eighty-four companies returned for the second time, another 17 for the third. Growing at all during these past few years of recession, frozen credit, uncertain markets, and depressed business and consumer spending is noteworthy. Growing fast verges on incredible. It was good to see companies such as Monoprice, Morgan Borszcz Consulting, Skullcandy, Triplefin, Walz Group, and all the others continuing to do so well. Hats off to everyone at those companies.

There were other companies that are first-timers on the list but not to Inc. or Like Pandora. When we first wrote about that company in an October 2007 cover story, founder Tim Westergren was trying to break out of perpetual start-up mode for his Internet radio site, which at the time had eight million listeners. This year, Pandora ranks at No. 253 with a three-year growth rate of 1,221.5 percent, more than $50 million in revenue, and 60 million true believers. If you come to this year's Inc. 500|5000 conference, September 30 through October 2 in Washington, D.C., you can hear this clever and creative entrepreneur speak on the subject of "How I Got to Profitability." Consider this a plug.

I also came across the familiar names ModCloth (No. 2) and Thrillist (No. 93); their CEOs landed last year on our popular list of "30 Under 30." It was good, too, to see StumbleUpon, at No. 126, though not all that surprising, given that we've called upon CEO Garrett Camp for tips on how to be more productive.

The rest of the ranking -- the other four-fifths -- comprises newcomers (the silvers, if I continue with the Girl Scout thing). Some have surprising histories, like the gunmaker Freedom Group (No. 217), which, 194 years after its founding, has 2,900 employees, $848.7 million in revenue, and a three-year growth rate of 1,360.8 percent. Then there's The Elf on the Shelf (No. 222), a company that sprang from a family's Christmas tradition.

The Inc. 500 is all about fast growth. From 2006 to 2009, our No. 1 company, Ambit Energy, grew 20,369.4 percent. No. 500, three-time honoree AtTask, grew 603.6 percent.

But numbers tell only part of the story. Behind the achievement of fast growth are CEOs whose success proves that no industry is too humble or too sophisticated for the truly ambitious. These are men and women who ferret out opportunities, unearth profitable niches, and then find confirmation of their ideas and strategies in the marketplace. Of course, they take pride in the achievement of fast growth. But if you read their stories in the pages that follow, you'll find that their companies are much, much more than engines of growth. They are expressions of what's important to them, of how they want to live their lives, engage their minds, treat other people, feed their families, and influence the world.

So in the end, it's not really about the numbers at all. But you knew that.