I don't know how many of you made these when you were kids, but me and my siblings tried it many times. We used tin cans with the sharp edges though (gasp)! I just knew my two would have a blast with these. I took two clean yogurt containers and poked holes in the bottom. I put a piece of yarn through the bottom of them and tied the yarn to toothpicks to hold it in place. This was a great science experiment in getting the sound vibrations to travel down the yarn. We learned that you need to hold the string tight and face the direction of the person holding the other cup. It was super fun!! My son was amazed and I am so happy I captured that on his face in the pictures.