You want to keep your skin cool and dry even in the hottest days. When you exercise, sweating reduces the surface area of your body that is exposed to air. Sweat evaporates from your skin quickly through tiny tubes called sweat ducts inside the pores of your skin, much like sweat glands do in other animals. But when excess heat builds up—like during a workout or while wearing a heavy jacket—your body makes more sweat than it can remove by evaporation alone. So this extra fluid moves into the spaces between cells (called interstitial space) and compresses slowly but surely against all those cells until it reaches its maximum density: 1 milliliter per cubic centimeter (ml/cc). This condition is known as hyperhidrosis, excessive sweating…and if you have too much of it, people will start thinking about sending you to one side or another!