A long time ago, when I lived in Arbroath in Scotland, my role before opening up the old Fleming Partners office was to do the school run. Our kids went to a small village school just outside the town itself and there was no bus.
On these runs I always tried to entertain the boys by talking about whatever came into my mind (and would not take more than 10 minutes.) So one day I explained why humans can see in colour and many animals can’t. This is because, I said, there are two types of vision receptor cells, rods and cones. Cones see colour and rods see brightness—monochrome, in other words. (I do know it’s a bit more complex than that, but these were primary kids.) Humans have both rods and cones, and many animals, like dogs, only have rods. So we see colour and they don’t.
This went fine and was met with all the usual approval that could be mustered from a 5-year old and an 8-year old.