The most important principle is "squash and stretch",[4] the purpose of which is to give a sense of weight and flexibility to drawn objects. It can be applied to simple objects, like a bouncing ball, or more complex constructions, like the musculature of a human face.[5][6] Taken to an extreme point, a figure stretched or squashed to an exaggerated degree can have a comical effect.[7] In realistic animation, however, the most important aspect of this principle is the fact that an object's volume does not change when squashed or stretched. If the length of a ball is stretched vertically, its width (in three dimensions, also its depth) needs to contract correspondingly horizontally.[8]