In its current state, Lightpaper is manufactured by mixing ink and tiny LEDs together and printing them out on a conductive layer. That object is then sandwiched between two other layers and sealed. The tiny diodes are about the size of a red blood cell, and randomly dispersed on the material. When current runs through the diodes, they light up. (via Rohinni’s Lightpaper Is Incredibly Thin, And Printable ⚙ Co.Labs ⚙ code community)