Transparent displays have been around for a very long time in the form of heads-up displays (HUDs) in aircraft and (to a limited extent) in retail displays, markets seen as too tiny by the large display makers and largely left to smaller firms and niche technologies. In the past two or three years, however, NanoMarkets notes that transparent display technology has been edging towards the mainstream. Keenly aware of the maturing liquid-crystal display (LCD) market's slowing growth trajectory, display makers are desperate to add new kinds of functionalities, even (or especially) if it means adopting another technology with higher-growth promise. On the demand side, new applications, such as the widening category of wearable computing devices, seem to call out for transparent displays.