Alumina Nanowire Mats & Tangles
When aluminum is anodized under carefully-controlled conditions, it can be made porous (like a honeycomb). If the pores are then exposed to an acid, the walls dissolve away, leaving behind a tiny alumina "thread" (nanowire) of about 10 nm diameter (10,000x thinner than a human hair!). This image shows what happens when a carpet of these nanowires is closely-bunched it forms tangles. You can't even really see the individual wires here, but you get some pretty neat matting patterns.