Watch how two architects use 3D printing to build new coral reefs and address California’s housing crisis. When architects Ronald Rael and Virginia San Fratello (who work together as Rael San Fratello) became interested in 3D printing, the technology was too expensive for them to use, so they hacked printers and developed their own materials. “One of our goals is to make this technology accessible to more people. We have a bit of an activist agenda about that, and that is something that underlies a lot of our work.” While most 3D printing uses plastic, they have printed with locally sourced materials “that are recycled or upcycled or sustainable,” such as grape skins and seeds left over from the winemaking process, clay, salt, coffee grounds, sawdust, and rubber car tires.