This article sheds light on the fundamental physics that accounts for the similar behaviors of heat transfer and fluid friction as the configuration of the convective flow system changes. Three methods are used, and as the methods change so does the configuration (design): complicated (bundle of finned tubes in cross flow), elemental (single body in uniform flow), and even more complicated such that it resembles a saturated porous medium. The configuration evolves such that it conveys the explanation better, more effectively. The article illustrates the essential role of evolving configurations in thermal-science fundamentals and practice. It shows that three methods (i.e. three designs, from purposeful changes in design) are better than a single method (one design). Science marches forward in this manner, and, at the same time, there is a creative reassessment of past advances. The purpose of looking back is to construct a single edifice that is general, simpler and easier to use.