What shrinks 100 percent cotton?

100 percent cotton shrinks primarily due to the natural fibers' reaction to heat and moisture during washing and drying. When cotton is exposed to hot water or high heat in the dryer, the fibers contract, leading to shrinkage. Pre-shrinking processes and washing in cold water can help mitigate this effect, but some shrinkage is generally unavoidable. To minimize it, it's best to wash cotton in cold water and air dry or use low heat settings.