If you live in a hard water area like I do, you'll probably suffer from limescale build up in your kettle. It's unsightly, and causes the kettle to be less efficient. You could of course buy one of the nasty commercial descalers, containing who knows what yucky chemicals, but there's an easy homemade descaler that works brilliantly. Citric acid. And if you can't find any locally from a home-brew shop, try eBay, which is where I bulk buy mine from.
If you want to turn this into an interesting home-ed science experiment, then you can (carefully) leave the kettle lid open and stand back and watch the limescale dissolve. Of course children should never be left unsupervised near hot liquids, and it's entirely at your own risk whether you choose to observe this simple chemical reaction or not.
Either way, you'll end up with a super duper clean kettle.
While I was descaling the kettle, one of these landed on the cupboard door, and I managed to dissuade the cat from trying to catch it long enough for me to grab a photo of it. Just be grateful I didn't remember to take a "before" shot of the kettle. It was really acky.
Until next time.