Our eyes are wonderfully complex biological devices, which most of us take for granted. But do you know that our perception of detail varies massively across our field of view? Or understand why we can walk in the dark but not read? This interactive cartoon does a great job of explaining those complex ideas and more, very, very simply.
Put together by Randall Munroe over at XKCD, it wonderfully explains night vision, color perception, detail, and even weird things like floaters and blue-sky sprites. I guarantee that you will learn something form reading it, that's for sure (click on the image for a larger version).
Perhaps the best bit is that it's interactive. It lets you explore some of the concepts it describes by looking at the image from a specified distance—which you can measure using a roll of paper. I dare you to give it a go in your open plan office. [XKCD]