Simply stitching together some nucleotides into a looong thread of DNA, was already astonishingly complicated. Endless DNA chains have their own unique problems, such as torque. The chromatin-forming histones, the topoisomerases, among many other proteins, take good care of our DNA threads. Leaving the covalently linked DNA aside for now, we want to look at how some biological systems align themselves. How is it possible, for example, that some seemingly boring lipids form stable and complex biomembranes? Finally, we want to get a glimpse of understanding of how peptide chains spontaneously clot together into highly complicated proteins. A common theme is that complicated systems can quickly emerge from relatively simple components. It is crystal clear: The structure determines the function (◘ Fig. 4.1). But then what determines the structure?