Last night Nico noticed that images in mirrors are backwards. Well, he noticed the letters on his shirt were backwards in the mirror, and asked me why. I didn't have the perfect, scientific explanation for him, but I did my best.
First I told him that the light is reflected back at you in the same spot where it hits the mirror, which makes it appear backwards. I told him to go stand in front of the mirror and hold up his left hand, and his reflection would appear to be holding up its right hand. Of course he tried that, and then came back out and said no, my reflection was holding its left hand up too. So I had him stand facing me while holding up his left hand, and then said, now I am going to raise my left hand. When he saw that my left was on the opposite side of his left, when face to face, he understood, and checked the mirror again. Sure enough his reflection is holding up it's right hand.
Then I took a piece of paper and wrote his name on the top, and on the bottom wrote his name backwards, and had him hold that up to the mirror. In the mirror the name on top is backwards, while the one on the bottom is not. He thought it was awesome, how they seemed to switch places in the mirror.
A single question, a simple explanation, and a couple quick experiments, at close to midnight last night, and Nico now has a better understanding of the world around him.