According to science fiction, transparent displays are what we will all be using in the future. Obviously before we can arrive at such a future, we need to first develop the required display technologies. Currently we have a few at our disposal, each with their own advantages and disadvantages, and now MIT has added another to the fix.
This new display technology is actually very clever in how simple its concept is. Instead of trying to rely on expensive, transparent electronics, or directly bouncing light into a user's eyes, it uses carefully tuned nanoparticles. By embedding silver nanoparticles just 60 nm wide into a piece of glass, the researchers were able to create a material that only reflects a specific frequency of blue light. That means a projection of the same color will be reflected off of the material, but all other colors can pass through, unaffected.
What the researchers built is a proof-of-concept without any optimization. They do believe that with further work it should be possible to create a full-color, RGB system, without sacrificing transparency. It is also possible the technology could be built into plastic sheets that someone could buy and place on any window they wish, making it into a transparent display, with the appropriate projector.