I was helping Emmet get dressed one morning -- pull-on pants, no-button shirt, slip-on shoes, etc. -- when we had the following exchange:
Emmet: Mom, did you know that light isn't really matter? It's really just an idea, even though it can affect matter through radiation... (continues in this vein for a while)
Me: Go to the potty, Emmet; we'll talk about particle physics when you're done.