There are certain things that every generation thinks it invented when, in reality, those "inventions" have been around for decades. TT bikes are one example, as every 10 years the same overwrought designs resurface in a blaze of non-race-legal glory. The humble base layer is another example, and the Giordana Wool Blend Women's Short Sleeve Base Layer proves the point with a reliance on the same material used for generations. It's made from Mimosa fabric, a blend of three materials that all warrant the "wonder" appellation in their own right, but the headliner is obviously the time-tested merino wool. Merino is a cycling staple that may no longer define the top racing jerseys and shorts as it did when all bikes were steel and cassettes were nowhere near the double digits, but there's a good damned reason why we continue to turn to it when the weather turns toward winter. It's breathable, it's the original hollow-core fabric, it stays warm if it gets wet, and it's naturally odor resistant. Every material used in cycling kit breathes and chances are good that you'll be wearing an anti-weather top in inclement conditions, so the real standout qualities for wool are the way it insulates and the odor resistance. There are a glut of synthetics in the base layer industry described as hollow core yarns, and wool is the reason why. They're all trying to mimic wool's ability to trap countless tiny pockets of air in order to create a microclimate of warmth, and--though they've basically succeeded in copying it--wool is still the original. It also stays warm if it gets damp, so you won't pay as steep a price if you over-layer and overheat during winter climbs. This timeless material is supplemented with nylon, which holds its shape and offers more support than wool, and spandex, which helps the four-panel construction disappear under mid and outer layers by stretching as appropriate.