At the beginning of 2012, I set out to form The World's Greatest Growth Portfolio.  Though I can't promise it will always live up to its moniker, the portfolio has returned 23% in just 11 months, beating the S&P 500 by about 9 percentage points.

A few weeks ago, I outlined  exactly how I would go about building my portfolio for next year: Invest first and foremost in companies that demonstrate exceptional levels of innovation, with special emphasis given to those that I believe will be around decades from now.

Today, I'm going to look closely at 3D Systems (DDD 2.36%). Later, I'll be looking at its main rival, Stratasys (SSYS 1.43%), to compare each company's strengths and weaknesses.

Read all the way to the end, and I'll offer access to a special premium reports on one of the companies that dives much deeper than I can in just one short article.

Before getting started, though, it's important to know exactly what 3-D printing is. To read an article on the basics, click here.  Or if you want a visual example of what the technology could be someday, think about how the main character was reconstructed with a machine in the cinematic hit The Fifth Element.

Did I make an error?
Last year, I left 3D Systems out of my portfolio. My reasoning was simple: I didn't like the rapid pace of acquisitions the company was carrying out. Over the past few years, 3D has acquired all or part of Viztu Technology, TIM, INUS Technology, Z Corp, and Vidar.  Call me old-fashioned, but I like it when a company that desires to grow is able to do it organically, rather than by buying up the competition.

But as far as 2012 has been concerned, my fears have proved unfounded. For the nine months ending in September, 3D has managed to increase revenue by 57%. That has been tempered by the fact that net income grew by only 2.2%, but savvy investors know that this is due mainly to a heavy increase in selling expenses, as the company offers higher commissions to its growing staff to go out and sell its products.  

The end result? The stock is up more than 215% so far this year.

The meat of the company
To dig a little deeper, we can explore what gives 3D Systems an edge in the field of 3-D printing. The company is trying to get personal tinkerers hooked on 3-D printing with the launch of its Cubify.com, which allows individuals access to design tools and a platform to show off their inventions. In addition, Microsoft's (MSFT -1.84%) Xbox 360 can now be used as a 3-D scanner -- which kind of blows my mind.

For those willing to shell out the cash, 3D now offers a personal 3-D printer called the Cube, which goes for about $1,300. That may be high now, but if the evolution of personal computers is any indication, prices could easily come down with popularity.

3D is also making serious inroads into specialty business industries. The acquisition of Z Corp gives 3D Systems inroads into the architectural and automotive industries. And just last quarter, health-care buyers accounted for 13.3%  of all revenue, as the printers were used to make things like hearing aids and dental crowns for patients.

What's the bottom line?
In the end, I'll admit that there's a lot to like about 3D that I may have not given it credit for from the start. In fact, Chris Anderson, editor-in-chief of Wired magazine, has pointed to 3D Systems along with Autodesk (ADSK -2.00%) as two big winners in the 3-D printing revolution.

I'm still a little wary of all the acquisitions, so if I include it in my portfolio for 2013, 3D will probably get the lowest allocation -- but there's no telling how big that could grow over time.