Imagine you hit a button on your printer, and out emerges a prototype of a prosthetic leg or a component for a space shuttle. The moment has arrived, and it means big things for 3-D printing companies. One Dutch architect even has plans to print a 1,100 square-foot house. The European Space Agency is looking into building a lunar colony with a 3-D printer that uses moon dust.
Looking to get started? Design your products for the aerospace industry and the medical sector: Those will drive the most growth, with the greatest profit potential. "Companies are going after markets where the volumes are relatively low and the value and complexity of products are high," says Terry Wohlers, president of Wohlers Associates, a consulting firm.
How big will it get?
The market could reach $3 billion—that's Global Industry Analysts's worldwide projection for 2018.
(Read more: 3-D Printing Sparks Innovation Among Small Companies)
How much do I need?
You'll need capital. How much depends on your ambition: $20,000 to $600,000 for a commercial printer, if you want to make aerospace parts or prosthetics. A $500 version will do for toys or necklaces.
Who's in it?
There are big incumbents. Stratasys controlled 56 percent of the market in 2012. Venture capital-backed Shapeways is the leader in on-demand printing.
(Read more: Made in the USA: More Consumers Buying American)