How Does a Piano Make Sound?

Hello Willard Wildcats!
We have been thinking about how musical instruments make sound. They all vibrate to make sound, but where are the vibrations? Some instruments you hit to make them vibrate, like drums and cymbals. Some instruments make sound because air moves through them and vibrates, like a clarinet or trombone. And some instruments make sound because they have strings that vibrate.
But what about a piano? It looks like you hit the piano keys to make sound, but you can't see inside a piano to see what is happening.
In this video I open up my piano so we can see how it makes sound!