This amazing interactive model has been floating around for a while, passed along via Facebook and other social networks. It presents different organisms, buildings, and planets to scale so that you can see their relative size differences. You start at the level of a human, but can scroll to zoom in to the level of strings (the quantum kind, not the yarn kind), or out to the non-observable universe. It’s quite a journey! Each object that is shown can be clicked on for an explanation (which is a good thing, because I had no idea what quantum foam is).