Today we sweat in P.E class and when we sweat we are cooling our body. Sweat comes from these leittle particles that are stored under your skin, after your body does a lost of physical activity (exercising for example) those sweat glands multiply, and they need to go somewhere, so they go through the skin on to the outer layer, and after that, the sweats need to evaporate, or washed off, that is why being in a cool place removes the sweat.