Women’s long underwear tops are made for comfort and styled to fit any body shape. Women’s long underwear tops, also called base-layer tops, keep the body warm by wicking moisture away from the skin. Sweating in cold weather makes you even colder, so women’s thermal shirts work to wick that moisture away. Women’s base-layer tops and thermal shirts trap a layer of warm air next to the skin, which keeps the body warm. Women’s long underwear tops from brands like Ice Breaker, Hot Chillys and Kenyon offer extreme comfort and warmth.