Nano is short for nanotechnology, which essentially means miniscule stuff and / or the manipulation of individual atoms and molecules, which is way beyond our comprehension. Patagonia have utilised a highly compressible, low bulk and hydrophobic PrimaLoft Gold Insulation Eco, in order to make the Nano Puff vest an extremely lightweight and slim piece, ideal for layering with excellent heat retaining properties. Packs into the internal pocket, making it an ideal travel piece which will come in useful all year round.