What is the difference between the human genome and a pair of headphones?

If you've ever put a pair of headphones in your pocket, you'll know how difficult it is to keep a long cord in a bundle without getting it hopelessly tangled and knotted. You'll also start to appreciate the monumental challenge that our cells face when packaging our DNA. At 2 metres in length, the human genome is longer than the average human. But in every one of our cells, the genome needs to fit inside the nucleus, a tiny compartment just 6 millionths of a metre long. How does it do it? One of the secrets behind this monumental feat of folding has just been revealed by research that shows the human genome's three-dimensional structure. A team of scientists led by Erez Lieberman-Aiden and Nynke van Berkum found that our genome folds into a shape called a "fractal globule", where the long strands of DNA are densely packed but without a single knot. It's an awe-inspiring feat of space-saving and keeps DNA accessible. When a particular gene is needed, the DNA it sits on can be easily unpacked. Lieberman explains, "The best way to think about it is that it looks like a pack of ramen noodles when you just start cooking them: really dense, but totally unentangled, so you can pull out a noodle or a bunch of noodles without disrupting the rest." Previously, scientists suggested that the genome folds into a more tangled structure called the "equilibrium globule", which is more like ramen noodles post-cooking - a massive knotted mess from which single noodles are difficult to extract. Until now, the fractal globule was a theoretical shape that existed only in the minds of mathematicians. This is the first time that it has been observed in reality. The shape was first described by a mathematician Guiseppe Peano in 1890 and in 1988, Alexander Grosberg proposed that a long molecule might spontaneously fold into such a shape under the right conditions. Still, it took till this week for anyone to observe a fractal globule in reality. "[Peano] had no idea that it described any actual object in the universe," says Lieberman-Aiden, "but it turns out it describes the genome!"