A harmonica is a fun little instrument that looks like a rectangular box.
It has several small holes on one side.
When you blow air into these holes or pull it out, the harmonica makes different musical sounds.
It's like when you blow on a straw and make a noise. But the harmonica helps you make even nicer music!
You can play it by just using your breath, and it can create happy tunes or even sad songs!
Isn’t that cool? You can try it by finding a harmonica and blowing or drawing air through those holes!