Under Armour’s mission is to make all athletes better through passion, design and the relentless pursuit of innovation Where we started? It all started with an idea to build a superior T-shirt The technology behind Under Armour's diverse product assortment for men, women and youth is complex, but the program for reaping the benefits is simple: wear HeatGear when it's hot, ColdGear when it's cold, and AllSeasonGear between the extremes. Warning: This product can expose you to chemicals including chromium (hexavalent compounds), which is known in the State of California to cause cancer and birth defects or other reproductive harm.