Seven-year-old Faith Lennox never thought she needed a left hand; after all, she couldn't remember losing hers when she was only 9 months old.

The 7-year-old, grabbed the replacement as soon as it came off a 3-D printer on Tuesday in Los Alamitos, California. She put it on and raced off on her bicycle.

Later, Faith happily showed off the hand to others, flexing its pink and blue fingers as she gripped her small, stuffed 'Finding Nemo' fish.

The prosthetic was constructed overnight at the Build It Workspace studio. It represents a breakthrough in small, lightweight hands that are economical and easy for children to use.

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She doesn't need any help: Faith Lennox, 7, right, smiles as she holds an extra plastic prosthetics part with her newly 3-D printed hand at the Build it Workspace in Los Alamitos, California on Tuesday

A new addition: Faith Lennox, 7, adjusts her newly 3-D printed hand which is the result of an emerging technology that is revolutionizing prosthetics

But when it came to getting one custom made in a day by a 3-D printer, that was a different story. Particularly when she got to pick the colors — her favorite pink, blue and purple, like the ones on the tank top she was wearing. It didn't hurt, either, that the appendage, called a robohand, looks a lot like the pair Marvel superhero Iron Man wears.

'It's really cool!' the otherwise shy little girl said with an exuberant grin as she stood surrounded by high-tech computers in the Build It Workspace in this Orange County suburb on Monday.

Build It Workspace is a 3-D printer studio that teaches people to use high-tech printers and provides access to them for projects. It also does commercial printing.

She had gotten out of school early to go there with her mother, Nicole, to watch in fascination as her new hand began to take shape.

She stood for several minutes transfixed as it slowly moved from computer image to hard-plastic reality.

The finished product will be the result of an emerging technology that is revolutionizing prosthetics, said Build It's Mark Lengsfeld, especially for children like Faith, who quickly outgrow expensive prosthetic limbs and have trouble even using them because of their size and weight.

Many functions: Faith Lennox, 7, rides her bicycle with her newly 3D printed hand outside the Build it Workspace parking lot on Tuesday

Cool tricks: Greg Lennox holds a 'Nemo' plastic fish as his daughter Faith grabs it with her newly 3-D printed hand as her mother, Nicole and Build it Workspace president, Mark Lengsfeld, looks on

'It's an amazing thing to be doing,' the company's president and founder said of making a hand that weighs less than a pound out of the same kind of plastic used in automobile parts.

Although Lengsfeld's company has printed out everything from pumps for oil and gas companies to parts for unmanned aerial vehicles, this is the first hand he and his three employees have built.

Airwolf 3D, whose printers built Faith's hand, recently cranked out 200 hands for children around the world as part of an international competition to see which company could use the most 3-D printers in one space at one time. Airwolf, with 159 printers going, won by one, said the company's creative director, Tyler Caros, who was keeping watch on Monday as the hard plastic going into Faith's hand slowly unspooled.

In love with her hand: Faith Lennox, 7, left, forms a heart with her newly 3D printed hand on Tuesday

Going for a ride: Faith Lennox, 7, adjusts her helmet before riding her bicycle with her newly 3D printed hand outside Build it Workspace in Los Alamitos, California

The oldest of three children, Faith had compartment syndrome when her position during childbirth cut off the flow of blood to her left forearm, irreparably damaging tissue, muscle and bone. After nine months of trying to save the limb, doctors determined they had to amputate just below the elbow.

Faith's parents were working with the nonprofit group E-Nable to get her a 3-D-printed hand, but the technology is so new there's a waiting list, her mother said. Then she learned of what Lengsfeld's company could do from a friend whose son visited with his Scout troop.

E-Nable provides open-source technology for building the hand, Lengsfeld said, making it economical for anyone with the right printer and a set of instructions to create one. Faith's only costs $50, and when she outgrows it she can easily build a bigger replacement.

'It's been an honor to help her,' he said.

The little girl who taught herself to swim at age 3 and surfs with her father already knows what she plans to do when she puts that new hand on.

'Ride my bike!'she said with a big grin.

Although she's already a competent rider, she noted that making turns with just one hand can be a little tricky.