 So let's assume you want to figure out the pH of a solution. But you don't have any limous paper. Hmm, what could we do? Well, there is a solution. Many fruits and vegetables contain a substance that changes the color depending on the pH. So let's prepare such a solution out of red cabbage. The process is quite simple. You take some red cabbage, cut it in pieces and put it in boiling water. Almost immediately the water will become purple. So let's cook it a bit more and then we're going to try to remove the cabbage so that we only have the purple liquid. You don't have to throw away the cabbage, you can actually eat it. Now it's time for some experiments. Here I have three solutions of which I don't know if they're acidic or if they're basic. So I'm going to add some of my solution. If it turns very red, I know that is a very low pH, meaning it's acidic. If it turns blue or almost green, that would mean I have a basic solution with a very high pH. Let's have some fun and see what happens if I put my most basic solution and mix it with my most acidic solution. As this was a bit fast, let's look at it again in slow motion. So we start with our almost greenish basic solution. Once the acidic solution comes in, the acid and the base react with each other in a quite violent way and do what we call a neutralization. So that's it. We created our own acid base indicator.