Outdoorsmen actually used to wear a scratchy wool baselayer intentionally, to stimulate circulation. We're not into that. Paradise is ultrasoft, highly breathable and moves with you just about as easily as another layer of skin. It lives up to its name - nothing's softer or performs better against your skin. First Ascent Guide Melissa Arnot says it's "so fitted and so silky, I forget it's there." Of course it's also moisture-wicking, quick-drying and, for the sake of your tent mates, resistant to odors (no offense). Machine wash.