We live in a world of fluids—air, water, blood, gasoline. In fact, fluids are so vital and familiar to everyday life that one can easily take their varied and fascinating properties for granted. Many household products exist because they make use of some exotic flow phenomena. A cookbook is a storehouse of fluid facts. Our industrial civilization began when the change of water to steam—really an extraordinary occurrence in its own right—was appreciated and applied. Fluids, then, have intrigued scientists for hundreds of years and their diverse behavior means that their study is rich in concepts and models and draws upon and contributes to many fields; it is truly multidisciplinary, in fact.