10 Things You Didn't Know About Everyday Objects

Have you ever wondered why pens have a small hole in the side? It turns out that there is a good reason for this. For example, if you travel by plane and the air pressure changes, without this small hole the pen could ruin your journey by filtering into the pocket of your favorite jacket or literally exploding. Often we do not realize how well studied the technologies behind some objects we use every day. Even a common pen has a couple of secrets. So here are 10 everyday things with unexpected features.