The heat goes on! What is HEATTECH? HEATTECH is an innovative fabric that generates heat from your body. HEATTECH fibers capture the energy of water molecules emitted from your body and convert them into warmth! Wear them for easy layering or as an everyday shirt! Available in stores and online at Uniqlo. com. #Uniqlo #Uniqlousa #heattech #TheHeatGoesOn