Rotaxanes

Okay kiddo, let me tell you about something called rotaxanes. Imagine you have a toy train on a track, it can move back and forth along the track but it can't come off the track. Well, imagine there's a little cartoon mouse running around on the train. It can move back and forth too, but it can also climb up and down a little pole that's sticking up from the train.

Now imagine that the train is made up of two parts. One part is like the track and the other part is like the little pole. But they're not connected together like a train and its tracks, they're just hovering next to each other in mid-air. And the mouse can still climb up and down the pole, just like before.

These two parts are actually molecules, which are super tiny things that make up everything around us. They're stuck together in a special way so that the molecule that looks like the track is really long and skinny, kind of like a piece of spaghetti. The other molecule, the one that looks like the pole, is a little round thing with a hole in it, kind of like a donut. The skinny spaghetti part can thread itself through the donut hole, kind of like how a bead can be threaded onto a string. When the spaghetti part is threaded through the donut hole, it makes a little structure that looks like a tiny toy train with a little mouse on top.

Scientists call this type of molecule a rotaxane, which is a fancy word for a molecule that has one part threaded through another part. Rotaxanes are really interesting because they can be used to make tiny machines, like a little toy train that can move or even open and close its doors. Cool, huh?