Electron spin makes us picture electrons as if they "spin" like a tiny toy top spinning on a table. But here’s the thing: electrons don’t spin like that at all!

In the article Electron's spin - Part 1, we discovered that scientists once thought electrons might be spinning, so they gave this special property the name spin. But later, they realized electrons don’t move like a ball or a top at all.

So when scientists say an electron has “spin,” it’s just a way to describe something unique about it. It helps us imagine the electron having a direction — like pointing up or down — even though there’s no real spinning happening. It’s more like a special property that only electrons and other tiny quantum particles have. However, they can flip their spin up and down, just as Millie observed in Book 1.