It is simple to knead a piece of paper into a ball of paper, but the dynamic mechanism behind it is very complicated. When paper is wrinkled, it will form an intricate crease net. Although the paper will bend along the existing crease first, unless the folding order is exactly the same as before, a new crease will be formed every time the paper wrinkles. At present, it is not clear whether it is possible to predict the way a smooth piece of paper wrinkles to form a paper ball.