How does nonlinearity manufacture fractals and chaos? There is one and only one answer: #stretching and #folding. All flows and all #maps that manufacture fractals do it by stretching and folding. Let’s look at a simple example. Think of a pastry chef making a #croissant. She puts down the dough and stretches it with a rolling-pin. Then she puts a layer of butter on it and folds it. She rolls and stretches it again, puts another layer of butter, and folds it again. And so on ad infinitum, or almost. What you get is an object, a delicious croissant, which is a fractal in the direction perpendicular to the table, with a very large (quasi-infinite) number of layers. This is the way all dynamical chaos works!