I blogged a couple of months ago about the amazing future of 3D printing. The real power isn’t in the technology itself, but in the increasing affordability of 3D printers, which promises to democratize innovation and manufacturing. Today’s story is one of a South African carpenter joining up with a Washington puppeteer to create prosthetic hands. Their 3D-printed product has already benefitted more than 100 children—at no charge. They have also made the design and instructions available online, so that any person in the world with an internet connection, a 3D printer and about $150 in parts can print a prosthetic hand. The two met through YouTube and collaborated through Skype. This is a development that—in many respects—was impossible ten years ago. And it is possible now only because innovators and entrepreneurs have paved the way, and free competition has driven down costs. A similar story comes out of 3D printing firm Stratasys, which a child gains the ability to use her “magic arms”: While most consumer-grade 3D printers today advertise the ability to print small toys and decorations, their potential is endless. Once they become a common household product, they will follow the pattern of desktop publishing and audio recording: a lot of junk, but also a lot of useful tools that will change our lives and turn carpenters into medical heroes.