We're still looking at another 3 to 5 years of development here, but transparent OLED lighting panels are definitely on the way. This 12-centimeter prototype panel developed by Philips Research is transparent until flipping the switch for illumination. Unfortunately, the panels are currently limited in size due to complexities in the manufacturing process that necessitate a clean-room environment. Ultimately though, larger panels will replace "dumb glass" in household windows and stall dividers in trendy Germany toilets. What, haven't been to Berlin lately?