Fun is to stack containers; then watch them tumble!

I was down the hall and looked over to see that Eva was attempting to stack the fourth (4) container on top of three she had already stacked. I helped her with the fourth as she had a larger container she was at first trying to stack on the smaller ones and it wasn't going to work. Then, to my surprise, she stacked a fifth one. I put another on and it was so much fun and amazement to then watch them fall once Eva push the middle of the stack.