Perhaps not as famous as the double helix of DNA, the triple helix is just as useful and 50% more helical. It is the structure of the collagen molecules that make up a big part of our bones, teeth, muscles, skin, and various other bits. The triple helix shape helps to make it strong and tough, a bit like the twisted fibres of a rope.

More importantly, the triple helix is the path followed by the feathers on an arrow, so when my archery coach says “visualise the arrow hitting the middle of the target” I see something like this.