I've told my students that the world appears to us as it does because we happen to be the size we are. I've suggested that were we considerably smaller, say, the size of an atom, the world would look much different. What appears solid, for example, would not seem solid at all to an atomic-sized creature (if such a thing were physically possible).
As something of a follow-up to that discussion I thought I'd repost this link to a fun interactive site that you'll find difficult to stop playing with once you start. By moving the scroll bar you can zoom in or out to see how big the universe is compared to our planet and how big we are compared to the smallest parts of an atom.
As you scroll toward the very small notice that it seems as if what we call matter simply ceases to exist. All there seems to be at the most fundamental level are hypothetical entities called strings - incredibly tiny filaments or wisps of energy. But if there's no material substance at the heart of reality is matter just an illusion?
Give the interactive site a try and spend a little time just being amazed. It may take a few seconds to load so be patient.