If you are moaning once again about your suitcase being far too small as your vacation approaches, you should take human sperm cells as an inspiration. During their production, they are faced with an almost insoluble task. They have to pack 23 DNA threads with a total length of one meter into a head with a diameter of just three thousandths of a millimeter. And in the process, the delicate threads must not become entangled in an inextricable knot, nor must they tear.