What makes clothes shrink?

In nature, elements generally expand when heated and shrink when cooled (with the exception of water). If so, then why is it that clothes shrink when washed or dried in too warm a cycle, instead of maintaining their size or even get bigger?

Best Answer chosen by Asker:

Of course it depends on the fibers involved. There are two kinds of shrinkage. Progressive shrinkage occurs when the fiber itself shrinks. Wool fiber shrinks a little more each time it is washed, which is why wool is usually dry cleaned. Relaxation shrinkage is when the fabric shrinks. It is caused by the tension applied to yarns and fabrics during construction. The tension is released when the fabric is washed or steam pressed, causing it to shrink to its natural size. Most cotton fabric shrinkage occurs during the first wash. Also, fabric shrinkage in repeated laundering occurs because of the swelling of the fibers in the washing medium. Because of this fibers move within the fabric structure during the wash cycle and are pulled together during the expulsion of the capillary liquid held by the fabric during spinning. Functional finishes or additives can prevent such undesirable effects. It is much more complicated than this and the science can be an entire education course.