The Industrial Revolution was founded on economies of scale, butthe next transformation in manufacturing may come from individualhouseholds. An additive (or 3D) printer is a desktop machine thatcan make customized physical objects from software and simple rawmaterials. This device promises to dramatically reduce the cost ofmaking and distributing tangible goods, but it could also sharplyincrease patent infringement. Indeed, 3D printers present a challengeto patent law that is analogous to the disruption of copyright by MP3files. This talk explores the implications of 3D printing for patents.