Today, 3D printers can already make (almost) anything, but what if they could do it in one second? I will show a series of research prototypes that speed up 3D printing, e.g., by allowing users to interact with their work piece during fabrication--up to several times per second. How might future versions of such machines change our lives? If the transition from 1950's mainframe computers to interactive PCs is any indication, adding interactivity to 3D printing might empower users to not only make anything they want, but also to make them more creative. But how will we get past the challenges corresponding to what we see in computing today, such as IP and sustainability issues?