Shrinkage is a change in dimensions across the length and width of the fabric after washing, usage, and when exposed to the relaxing of fabrics. Mainly shrinkage is of two types. One is minus shrinkage and the other is plus shrinkage.  Heat and water cause wrinkles. Heat breaks the bonds holding polymers in place within the fibers of a fabric. When the bonds are broken, the fibers are less rigid with respect to each other, so they can shift into new positions.